Depending on what length/configuration you want your barrel to be, a factory 357 should be easy to find - the 41 a little harder.
GB's TC Classifeds is a great place to watch for them - you can even post a "want" ad there. Ed's Contenders is arguably the best place to find used barrels for a good deal, and he's a nice gent to deal with. Custom's I have always selected SSK and Bullberry first, but the SSK's are pricey and lead times have become pretty long from the later - at least 4 months. Have heard nothing but praise for the OTT barrels although I've never had one myself (yet). Mike's work has become so popular that I hear his lead time is as long as Bullberry now though. I also heard the Virgin Valley boys are starting back up, so they may be another source.
Good luck with your TC - you're hooked!