I am fortunate to live in Preston, Lancashire (UK), within 2 miles of a major-league UK electronics distributor called CPC. They definately stock this type of adapter, cable lengths up to 10m. under the brandname "ProAudio" (which is a bit optimistic, it's looks budget to me) but they look very much like products of korea / china / tiawan so I'd expect them to be findable.

I have to agree that adapters = bad news, but if you have no choice you can find some serious quality 1/8 jack to phono cables in the "Home Cinema" sections; then get some phono-jack adapters.