I've used GAP Enterprises finger rests on G26 and G27's and like them a lot. I wouldn't want to be without them.
Concealable Control – Acquire. Retain. Perform.
However, they don't make one for the Shield. Their web page has stated that it's coming for about a year now. I've tried to reach them via email and it just bounces. I suspect they may be defunct.
I finally gave up and decided to make my own. I'm surprised how easy it is, and how well it came out.
I started by ordering a blank aluminum base plate from these guys for about $16.
Blank Plate for Smith Wesson s w Shield Mag Magazine Base Floor Plate 9 40 | eBay
I then found a appropriate thickness piece of aluminum (I chose 0.080" 6061) and formed it into the shape I wanted. I decided to make it long enough to cover the hole in the grip. I drilled a hole in it to match up with the hole in the base plate.
Then I got some Loctite Metal/Concrete two-part epoxy. This stuff is great, very strong and gives you plenty of time to work with it, at least 3-4 minutes. In addition it's relatively thick and gooey, so you can slide things around before it sets up. Within about 15-20 minutes it's already pretty hard. I filed/sanded off the anodized finish on the base plate, and roughed up it with 100 grit sandpaper along with the finger rest itself. I wiped them both down with acetone and glued them together. I didn't clamp them, there's no need, and the stuff is thick and sticky enough to keep things in place.
Finally, I gave it several coats of rattle-can matte black. I'm sure it will scratch off here and there (it's hard to adhere to aluminum), but it's easy to give it a quick respray when needed.
Here are the results.
Flickr
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https://www.flickr.com/photos/xtread...posted-public/
This same method would work with many hand guns. It only took a few hours of work, you might be faster if you have better tools than I do (like a good bench grinder or disk sander). And it only cost about $20 including the epoxy.