Are aftermarket car alarm Key Fobs the same (Viper alarm)

Hi

There is a Viper 350 HV alarm in my work van that was installed about 10 years ago by the previous owner , 

But I never got the Key Fob for it  

Viper website  had the manual download , and that says the Key Fob is 433 MHZ , which seems to be common , 

But are all 433 MHZ Key Fobs  the same ?  

I lose everything and would like to get a few of them programmed at the same time so I have a back-up , 

Has anyone here gone this route ?   I just do not want to pay for the Viper name if I do not have to !

Thanks for your help

I have no idea if the fobs are the same, but Viper, Avital, and Python are all under one company.

When my older Avital fobs died I found it was far cheaper to buy an entire alarm kit from Amazon with two new fobs than to replace one older fob.

When i got the new alarm it had the exact same plug on it so it took minutes to swap and reprogram.