As we’ve been mentioned, I’ll chip in, the options as I see them are:
Paragons – either the traditional slider or the new swinger, although the swinger may simply not fit the frame geometry.
2souls cycles
2Souls sliding dropouts by 18bikes, on Flickr
Ceeway do one – very similar to paragons you do gain a rack mount
Black cat swingers (probably same issue as with paragon swingers and availability issues over here)
or something like the Paul’s mentioned but you end up with a slotted disc mount which is no fun, if you’re going to do it, do it right
As far as I’m aware these are the only options available to framebuilders aftermarket and we can get all bar the black cats. If you want to discuss the merits of each design, email matt@18bikes.co.uk
Hope this helps
Matt