The Encore takes a STANDARD Mossberg choke, aka "Accu-Choke". also, Win-Choke or Browning Invector (NOT INVECTOR PLUS, be careful). I do believe the Mossberg 500 uses the Accu-Choke. For Mossberg chokes, just go straight to the horse:
http://www.mossberg.com/products/access.asp?type=chokes§ion=accessYou can see the difference on the Mossberg site, the choke on the left is an Accu-Choke (flush type), the 6th choke from the left is an Accu-Mag (flush type), so you can see a distinct difference in length. Be careful on the Turkey chokes, they call them X-factor or something, and make a model for both types of guns.
The Accu Mag chokes will NOT fit (I think the 835 uses these).
As far as I know, all T/C encore barrels take these chokes. I just ordered a T/C Turkey Barrel, but mine is Blackpowder! For regular shells, I'll use my pump or the 26" VR Barrel with add on sights (the 26" VR Barrel shoots too high at 40 yards in my opinion with the VR-Pattern is good with a Turkey Choke though)
Best thing, just take a choke tube with you and compare to the proper length.