You can mount that Radio Shack Mic by attaching it to the end of a peice of metal clothes hanger and then securing the hanger to the inside of your helmet with ultra-heavy duty outdoor foam tape like the kind used to mount mailboxes and stuff to the outside of your home. Also, put a small bend in each side of the hanger so that it cannot rotate when secured. Now you can bend the mic side of the hanger to keep the mic close to your mouth. I have also used pieces from the Lego Mindstorm kit to create a headgear for that mic.
As for the feedback with the RS devices, they do not give feedback when you use your head as a buffer. Mount the amp behind your head and the mic in front and that should stop the feedback while sending valuable electronic RF waves through your brain.
There, I did my good friggin deed of the day. Can I please do something obnoxious now?