Are you interested specially in the 450 bushmaster? The bullet diameter is the same size as any modern day .45 colt which is .452 in dia. Might open up a few more rifle options that could interest ya.
Anyway, Henry has break action single shot chambered in 450 bushmaster for $597.00
https://www.henryusa.com/rifles/single-shot-rifle/
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Guardian of the honey and nuts
Let's assume I'm right, it'll save time.