I happen to know that Thompson Center sells what I think you are looking for. Because I have it on one of my Hawkins Flintlocks. Is this the swivel kit you wanted?
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"Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, a total wreck, screaming Yahoo, with a big smile on your face."
That is exactly what I am looking for. I wasn't sure if this one would work on my traditions rifle. I found one on ebay that is model number 9700 and there are 2 other sizes. I just didn't know if that made a difference. I will just order one and see what happens...