Looking to add electric motor to my 29" mountain bike for less than $300

I found many kits for $200 but they're all 26" and the few 29" kits I did find are more like $400. Could I put a 26" kit on my 29" bike?

I just noticed the $200 kits say 85kg load capacity so I guess those are out as I'm 300 lbs. I might not even be able to convert my bike to electric for less than $300 now I'm thinking...