I recently spoke with John Forrister about getting a distributor in the UK (or at least in Europe) for the GTD gear especially with David's move and general push into Europe.
Apparently it has been on a Next Action list with their European franchisees for a while (more of a Someday/Maybe) but I have "encouraged" them to move it forward!
In the past I have just made sure I have ordered sufficient quantity from the States to make the shipping more manageable.
The only ones that could fit the bill are these -
Smead Waterproof Poly 1/3-Cut Top Tab File Folders
I haven't tried them but the fact that they're waterproof makes me think they would be very similar to the GTD ones. If you do try them then let me know (and others in the UK) whether they fit the bill.
Dave