Welcome to TC and to GBO. Most of the barrels made for G2s will fit your older frame. I have never had a compatibility problem going that way, but on a couple of barrels I had to polish the locking bolts going from an older barrel to a G2. The only TC made G2 barrel that you can't use on an original Contender is the muzzle loading barrel, and there are a couple of aftermarket barrels that will not either.
TC makes larger caliber barrels in the pistol calibers such as .44, .45 etc. that fit, and if you keep to trap door loads you can get and use 45-70. There are also some great larger wildcats that are used successfully with Contenders. With some of them you can take anything that you can hunt in most of the world. You can't use most of the larger rifle rounds like 30-06, 308, etc. If that is what you want you will need an Encore. The TC webpage
tcarms.com list of barrels will give you a starting point. If you google Contender barrels you will get a good idea about who makes the aftermarket barrels and what is available.
Word of caution: once you start with these things it is hard to stop. Seems like there is always just one more barrel you need...
