Don't know what the inserts you are talking about are, but machine work is expensive. Look for a local job shop in your area, but be prepared to spend some coin. Most places wont even start on a lil job like that for less than a few hours of work (need to pay for the machines).
Okay, just googled the inserts. Like scale inserts? Seems like you could just drill and tap these to fit? Am I missing something?