I got a bag of extra M5 long bolts from Fastenal. I just use them and cut them to length. The metal inserts are nice. Keeps the plastic from crushing even though you shouldn't really tighten them that much anyway. It is important to cut these bolts only 2-3 mm longer or you end up with the tip of the bolt pushing on the crank counter balance (DL-50/55, not sure about 30).