Brownells has complete 9mm uppers on sale now.
I bought 1-16" barrel from spinta precesion for $70 shipped and another 16" from classic arms for $75 shipped both were blemished not that i could tell.
I've built dozens of 9mm's, .40's, 10mm's and .45 AR's.
Easiest and cheapest way to do it is to buy a complete lower and then whatever upper you want. Palmetto State Armory has what they call "Dailey Deals" and often times you can buy the stuff cheaper already built than what you can parting it out.
Something of interest...
The 9mm lowers that take Glock mags will also take .40 mags. The .45 lowers will also take 10mm mags. IF you order a 9mm lower, you 'll just need a .40 S&W bolt along with a .40 upper and you are good to go. .40 uppers are scarce, they are an easy swap if you can change out the barrel.
Same way with the .45 lowers. If you get a complete .45, to change it to a 10mm, all you have to do is get a .40 Bolt and a 10mm barrel and swap them out.
Most of my stuff are SBR's but you dont need to go that route. You can use a Shockwave Brace and it will be classed as a pistol. They are getting very popular. They are fun to shoot, cheap, accurate and easy to suppress.
Heres a 9mm. Its showing a foldable Shockwave Brace on it.
Here's a .45. 10mm looks exactly the same. This one is an SBR
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |