The new Fang Trigger Guard from Strike Industries promises to make your reloads faster and more positive. It attaches in place of the standard trigger guard, fills in that annoying gap under in front of the grip, and provides you a short ledge at the rear of the magazine well that serves as a tactile reference point to index the magazine. This looks like it could work quite well, especially since I tend to find the back of the magazine well first before inserting the magazine.
The Fang does have one notable downside. It precludes the use of magazines with over travel stops like the latest iteration of the PMAG.
Check out the Fang Trigger Guard from Strike Industries.