youre probly looking for a g36 gearbox arent you?
if a gearbox would make it over the border you can try checking out this guys ebay store.
http://stores.ebay.com/Warthers-Originals
i bought a CA g36 gearbox from him for 80 dollars u.s. he might have more
a screw? seriously? why the hell would they seize a screw??
were they afraid they might get screwed or that somebody might assemble some random object?