i have a 48cc dualstart starfire gt-2 grubee from gasbike.net
it has a centrifugal and manual clutch and has pullstart and peddal start
it cost me $188 including shipping(i bought it when it was on sale and in stock)
i found it for you,but its just the motor $89(not the kit)it has cent and man clutch and pull and peddal start,you have to get the rest of the kit yourself(maybe buy another regular kit for$119 just for the other parts and spare engine? or buy the other parts separate to go with your engine.
its the first engine at top:
GasBike - Motor Only (MO)
also kingsmotorbikes.com also has them