I was thinking the same, try looking on bikes for shifter cables, and some brake cables and see if they match your throttle. I am doing it to my LawnFlite and When I get it finished I'll show you what I did but I didn't use a bike brake(im doing that on my Craftsman Lawnrider) I used the brake pedal off of an old Noma Lawn tractor and am going to use the brake cabble and drill a hole in the throttle cable plate(Or grind down the new throttle cable) so I can fit the new throttle cabble(its a thicker cable) and since there is already a spring at the pedal I shouldn't have to worry about finding a spot to put a spring.
My thoughts on the bike brake gas pedal is to find a way to use the original throttle cable and fit it on the pedal. Maybe check arild365's video on youtube, he might have it in more detail(im not sure I haven't watched that video from him in a while so Im not sure how much detail he goes into).