if the model of goped you said you had, which is the bigfoot, if i recall isnt a chain drive. you might have to convert it to chain drive which should be easy. here is a site where you can get all the parts you need for the conversion here as far as chains and sprockets for a goped: http://www.davesmotors.com/s.nl/c.885035/sc.12/category.27949/.f
for chains and sprockets, and here: http://www.davesmotors.com/s.nl/c.885035/sc.12/category.27954/.f
for wheel parts. theyre pretty good, but im not sure if they will do international shipping. you might have to ask and see.
that should be a good platform to convert nonetheless. the air tires should make a smooth ride compared to the sport models they make.