I'm in California and am buying an M&P 9 Compact. Here there is only one model available: the one without external thumb safety. I'm not set on it, but was wondering how possible it would be to add the external thumb safety to my version?

Just curious.

You can't do it. The parts required are restricted by the factory.

Check with Midway, and Brownells, as they sell many of the restricted parts. The Sear Block with the safety is available AFIK, but I have not seen the actual safety lever. You would also have to cut a notch in the frame. As a fellow Kommiefornian, I fell your pain. You would not believe the lengths I had to go to just to get a 9L here. Same problem, damn safe gun roster. In turning my 40 FS into a 9L, I needed many "restricted" parts. Between Brownells, Midway, Apex Tactical, and Speed Shooters Speciality, I was able to get them all...

I believe the frame is already has the cutout on all the M&P models. It is filled with a spacer for the no-thumb-safety models. Find a M&P armorer and he can order the parts and modify your gun.

If his gun came without a Thumb safety, His frame does NOT have the cuts on it. The cuts are rectangular. I have a M&P9 with the thumb safety and I used to own one without. Completly different frame cuts.
Here is a M&P with the safety removed. That is what the frame cut would need to look like....
http://i274.photobucket.com/albums/j...yHole-Left.png

Hope this helps.

The round "cutout" is for the Hillary Lock.... Just a plug with a flat area behind it.

The thumb safety requires some parts in the sear assembly and an actuator that looks a lot like (but isn't) the slide stop. I suppose you could add it, though, if you could find the parts....

Regards,

__________________
Stu.