What is the go to place for backup OEM parts and springs? Also, who are the major players in aftermarket upgrades for these? TIA

I just ordered and received some 2.0 Compact 4” guide rod assemblies directly from Smith and Wesson.  You have to call them.

They are pretty hard to find for sale for the Compact 2.0.  I’d previously ordered them from a 3rd party gun parts seller but they sent me the ones for the 3.6” barrel.

Otherwise, many of the other parts are compatible with other 2.0 variations and are easier to find.

Apex makes a variety of trigger upgrades for them.

Ebay actually has a few sellers who carry a lot of small parts.

ETS recently started magazines (17, 21, and 30 round) 9mm magazines for the M&P line.

Are there any specific upgrades you are looking for?

I've gotten a lot of parts (1.0/2.0, but all for the full sized models) from Numrich Arms and MGW.

gunpartscorp.com smith-wesson/auto-pistols-sw/m-p-series

midwest gun works smith-and-wesson-mp-compact/parts

For making the trigger better and tightening up the groups I've only used Apex for trigger kits and barrels.

apextactical smith-wesson

Thanks for the info. Really want to have a supply of oem parts for breakage/wear.  Just wanted to see what upgrades might be available if I decide to go that route.

Thanks for the listing of the S&W Parts.

Going to stock up now before Round 2 of Klung Foo...