Pics:
I found a picture online of a Koito headlight like mine, it looks about the same shape as yours: http://www.vjmog.com/ftopicp-32201-.html (scroll about 1/3 of the way down the page.)
It is marked 12 volts, but it uses a removable bulb so I suppose it could be retrofitted with a 6 volt bulb and socket. It also has a hole for a second smaller bulb just under the main one, I suppose for a parking lamp. It's about 6 inches wide by 5 7/8 inches high.
I joined the group and am waiting for approval so I can contact the seller.
Oops, two-year old post.
Besides Paul Miller there are a couple other places dealing in old Suzuki parts, I've had varying levels of success finding parts from these guys in the past:
http://www.andersonvintageparts.com/index.php
http://www.siriusconinc.com/product-nos_suzuki_parts-33.htm
http://flashyboyz.tripod.com/id12.html
These two are in the UK:
http://www.crooksclassicparts.com/
http://www.suzukisimon.pwp.blueyonder.co.uk/
I checked eBay and found a couple headlamp shells, but no headlamps. Of course, there are new auctions every day.
If you aren't able to turn anything up let me know - I could be convinced to sell the one I have. Like I said mine is 12 volts but it could probably be adapted with a 6 volt bulb socket and bulb.
The guy who is doing the final touches on my CB450 is turning an early 70s TS250 into a vintage motocrosser. He said I can have the headlight and hardware for nothing. I will give it a try.
That will be a different shape, but if you can get the whole assembly I wouldn't be surprised if it fits.
In reply to stuart in mn:
I can get the whole assembly and there was a version of the early 70s TS 250 with a D-shaped light. Not sure which one this has. The main thing is the distance between the forks. The spacing is narrow on the T250.
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