You're looking for an M3 5-6mm length screw (if you want the longer ones, the stock screws are 3mm IIRC) socket cap would be best. Lots of options for those on amazon.

http://www.amazon.com/Stainless-Socket-Internal-Threaded-Threads/dp/B00137FKCM/ref=sr_1_17?ie=UTF8&qid=1431544191&sr=8-17&keywords=m3+5mm+length

here's one supplier