I posted this earlier today on the Walther forum site. The specs on the M&P22 compact versus the Walther P22 are pretty much identical. Maybe this will help someone. Finding a holster for a gun with attached suppressor is not easy.
Posted at Walther site:
After a lot of looking, I found a nylon drop leg holster from Bulldog holsters. I have a P22 Q with a Silencerco Sparrow suppressor AND a Crimson Trace laser. The laser has a very small housing (model CMR-201)
The fit is perfect. It's model WTAC8-R. The Sparrow stays about half in the holster and the final 3" does come out the bottom of the holster. The fit at the holster bottom around the suppressor is snug so there is no wobble or looseness anywhere. There is an extra mag pouch on the spine.
I will be using this on my own property on a gun range course through the woods I have built. It's like a gun version of an archery 3D course.
All the other holsters I found were too awkward to wear at belt height with the suppressor attached to the P22. The bottoms were sewn shut, too small, too big, no extra mag pouch or had some other feature lacking. A search to find a Kydex holster to use with the suppressor came up empty. They were typically too short and provided no support for the suppressor so the whole gun wobbled a little. This Bulldog model holds the whole 11.5" gun snugly and is probably the best fit you will ever find without having a custom holster made.
The price is right too. Anywhere from $25-35 depending upon retailer. I bought mine at Cabela's in person after the clerk suggested this model and I verified the fit. The link below is a random ad for the item from the internet
Discount Hunting Supplies & Shooting Supplies, Ammunition - Able Ammo