YUP, been there, done that, and DO have the T-shirt
Take a yellow EAR plug, place it in the freezer,
http://www.ebay.com/itm/3M-COMMERCIAL-TA...6#ht_1634wt_986after it is cold, remove and stand up, slice it in half vertically.
Save one half, the other attach the flat part to the rear of the trigger guard,
double stick tape, other tape, any way you wish.
Problem solved
Mike
p.s.
OR buy this
http://www.hastingsdistribution.com/index.php?l=product_detail&p=49or
http://www.csmcspecials.com/Trigger_Guard_Rubber_Corners_p/corner.htm