companies like racetech make gazillions of springs and they have pretty good info on their website, if you call them up with your spring dimensions and a spring rate (lbs per inch of compression) they can tell you if they got something that will fit.
the k10's are pretty shitty forks, they are really heavy and the only reason people ever used them is they were dirt cheap, which they aren't anymore.
pocketbike forks, PW80 forks, TTR125, DT50, and even CR/KX/YZ80 forks are pretty cheap and easy to come by, if you pick a bike like the motocrossers that already has a 17 wheel its a lot easier.
you pretty much just gotta grab something and make it work. the longer forks like the dirtbike stuff you can shorten and add preload spacers to adjust spring rate, fine tune with oil level, pretty much no matter what you do its going to be way better than moped forks but its varying levels of fucking around and making spacers and stuff.