Nice score, a real Batavus moped!
Gaskets, clutch discs and miscellaneous parts can be bought here
These guysalso seem to have a lot of parts, just a shoddy website.
These engines were made with pedals, so if you really want to please all the pedalphiles you could.
Most websites are in Dutch and are run by old people who don't necessarily speak English, so if you need any help just PM me.