Unique bike search

Tunasister had a stroke when she was four years old. She has limited use of her right hand and leg. She also has two big dogs and likes riding while the walk alongside her. I know that sounds insane, don't question it, it works.

Right now she uses a crazy worn department store bike. It's suboptimal.

Ideally she needs a multi-use bike (capable of roads and basic off road) which is or can easily be configured to use only her left hand for shifting and braking duties, or even better, has a coaster brake.

This is weird and special, and I have found zero non-cruiser type bikes that fit this. GRM seems like the right place.

Obviously budget is a huge concern.

There are several companies that make three speed coaster brake rear hubs. You should be able to make them work with an old thumb/friction shifter on the left side. She'll have to get used to the "feel" of getting in in the right place. Probalby going to be a roll your own set up, but you should be able to convert about any cruiser type bike by building/buying the right rear wheel. 

Here's a non-cheap piece that might give you ideas on how to make a cheap version: The Paul Duplex Brake Lever

The term Hybrid bike or Touring bike may be what your looking for.  The Hybrid being that it is beefier somewhat like a mountain bike but without the aggressive tires making it more good for somewhere between paved to smooth dirt trails.  Not good at full "off-road".  Also, a hybrid is not as delicate as a road bike (good for pavement only.)  

I would look for a good, doesn't have to be new, Hybrid bike.  It will likely have 6 gears on the rear hub (could be as much as 8) and then 3 gears at the front crank.  6x3= 18 gear (speed) bike.  

A traditional bike will control the rear gear changes and rear brake with the right side controls.  But, you or a shop can covert this to the opposites.

On my bike the right gears are thumb-levers that are under the bar.  If I were to switch this to the other side, the brake would be normal and the gear changing would be a little awkward given that the levers would be above the bar.  Different than intended but not impossible to use.  

On my daughter's bike, moving the right to the left side would give you fine brake-ability.  Changing gears would mean rotating the knob the other way and the red indicator would be hidden from view.  Different than intended but not impossible to use.  

I would set the forward to the middle sprocket and just leave it there.  Most people ride in this gear anyway.  Make all adjustments to the rear sprocket's 6 gears now all on the left hand.  When the gears move to the left hand the rear brake will move to the left hand.  You can control a bike with just the back brake.  Actually, my 6 year old rides this purple 5 speed.  I have intentionally disabled her front brakes.  This then forces her to learn that the right hand is the rear brake and saves her from "ass-over-apple-cart" by wrongly using only the front while learning her first hand brake bike.  

Schwinn balloon tire beach cruisers has the 3 speed / coaster brake in the hub , 

probably 1980s-90s, 

They had a thumb  "shifter" on the handlebar but no idea how good that shifter worked,

I will keep an eye out for that wheel/hub at the swap meet.

Linus makes old-school bikes with coaster brakes, internal-geared hubs, etc. I have the Roadster--no speeds, no fenders, coaster brake. 

Some great ideas have been brought up in this thread so far. If you are searching the internet for inspiration, I'd recommend trying "adaptive cycling" "adaptive bike controls" and a few searches like that if you haven't already.

How about a Catrike?

With 1x10/1x11 drivetrains becoming fairly common place, there should be plenty of options in a variety of styles that could be configured to work if she can live with one functional brake. Avctually, the way I have my mountain bike setup, it could be ridden left hand only. Check out bikesdirect.com, they should have some decent options under $400, maybe less, although I don't know what availability looks like at the moment.

Not sure what part of a cruiser won't work but finding one with an internally geared 3 speed gives you a thumb shifter and a coaster brake. Add a decent tire and you can ride any terrain you wish.

I will recommend a bike most people hate. They were a sales flop so it will probably be hard to find but for grins look for a Trek Lime. It is a "comfort bike" with an automatic 3spd and a coaster brake. 

I bought one for the missus and she loves it. It is kind of the iPhone of bicycles.  

When I owned a bike shop I had a one armed customer. Built him a mountain bike using a rapid fire shifter and a grip shifter on the same side so he could have 21 speeds.

In reply to NOT A TA :

Brilliant. 

Thanks everyone! I'll suggest these and let you know.

Shimano Nexxus hubs go up to 8 speeds and I think they have coaster brakes too.