I have a P220 Super Match and a Match Elite. I was thinking how great these would be with a can on them, but I don't know if such a barrel exists for the 5 inch P220's in .45. Being less popular models I doubt it.

Does anyone know if these ever existed?

Have you checked with Sig to see if they ever made them?

Bar-Sto has a couple of different extended threaded 220 barrels listed on their website.
Aint cheap. $325.

Many years ago I bought my P220ST new right when they first came out. It has the rail in front to mount the compensator from the P220 Sport model.
I found a couple of the compensators for sale and bought them.
If the compensator is mounted you need a 5" barrel to use it. I bought a 5" barrel from SIG, it is NOT threaded but I would imagine a gunsmith could easily thread the barrel.
Call SIG. They could probably thread the barrel for you if you bought the 5" version from them.

Not sure if this could be made to work for you so please check before buying, but over at Numrich:

http://www.gunpartscorp.com/products/2082740