If you like spending money the TP9 is for you... unfortunately everything cool for the TP9 is made by B&T and currently hard to get ahold of.. like the suppressor which can be had cheaply but the production numbers are low. Resale value is insane. I personally dont know what other 3lug attachements fit on.... i dont think anything does that isnt specially made for the TP9. The only other barrel attachment ive heard of someone putting on a TP9 is a suppressor made by Thompson machine... i dont know much about it.... tbh i was going to contact them to see if they even still can make them or not.
I can vouch for the customsmith aftermarket parts.. i have the TP9 with CSM side charging upper receiver, magwell enhancer, gen2 CSM trigger. They are all nice parts.