www.myowntuxedo.com has lots of tailcoats for very reasonable prices. The neat thing is they have the BIG sizes that are so hard to find in thrift shops. Also, you just buy the coat, not the pants, which is an additional benefit. They are very easy to work with. I've purchased several coats from them and have been very happy with all of them. Here is a photo of a "mock Montrose" conversion from one of their mandarin collar coats.