The best way is with a cast shroud that has no safety on it and then use a Bold or Timney trigger with a Remmington style safety and you can use a rasp or whatever tool you want to open up the side of the stock to use it. Lots if different folks sell the cast shroud for around $35 and then another $40 for the trigger. I think the name of the company that sells it is Sunnyhill, but I cannot remember off the top of my head right this second.
Otherwise, you can either buy one already machined for around a $150+ or you can machine your own with a milling machine and the cutter that Brownells sells with the kit.