Stevens 220A trigger guard

A friend of my son has a 220A with a missing trigger guard. The front screw is broken off almost flush with the bottom of the receiver. The strange thing is that the front screw threads in from the inside of the receiver. I have not seen this before. How can I remove the broken screw without disassembling the action? Also, where can I find a trigger guard and replacement screw at a reasonable price? I doubt if the gun has enough value to merit a trip to a gunsmith, but it has sentimental value to the owner. Any advice is appreciated.

Leon