Yeah, I had one done too.
https://i.imgur.com/Fiqiv8i.jpg
Basically bought a USC, then bought a UMP for donor parts, then had Tactical Excellence do the conversion (which was almost the cost of another rifle) and was able to have one firearm for the price of three.
The things we HK enthusiasts do to have something close to a correct HK firearm because lord knows HK will never be able to import one like this. Fortunately I was able to sell the extra USC and UMP parts which pretty much offset the cost of the actual build (eventually).
I remember the UMP suppressor was expensive and that sounds about right for my dealer price back then, but damn sure glad I grabbed one because you can't really find them now.
The UMP was a pipe dream since I first read about it in Soldier of Fortune in the 90s, never ever thought I'd have a setup like this one. And the opportunity to try and do it now is pretty much gone, especially if you want things like a factory HK barrel.
Most people are rolling Top Notch parts or HDPS parts.