Although those Stanley knife handles were made in both the U.S. and the U.K. I’ve a feeling that the saw blades to fit were only ever made in the U.K. Don’t know if they are made here now, or if they are the same quality they used to be. Very little that Stanley offer is.
They have been made for years, since the 1970’s to my certain knowledge, and certainly before Tim Leatherman dreamt up his tool.
They are basically just a pad saw blade that fits a Stanley knife, so you don’t have to carry two handles.
Leatherman tools are relatively popular here, but I can think of all sorts of things I’d cut with a £2 saw blade that I wouldn’t go near with a £100 Leatherman!
O.P. If you want one it’s probably best just to buy the blades and use a domestically sourced knife. There’s nothing unusual about the knife. I suspect shipping would cost more than the blades though.