Probably like every other of the 104 views before me I thought "What on earth is a fat boy strap?"!
Well - not I know the answer to that but still not much closer to where you might buy one. There are a few companies that stock western riding kit in the UK though. Perhaps try places like https://western-saddler.co.uk/ and https://thewesternshop.com/ Kramer do some western stuff - but not this. I suspect you might need to have one made.
