I know you can get these: http://www.chainreactioncycles.com/Models.aspx?ModelID=33951 for the obvious. However, can you purchase similar items which essentially allow for a full outer guide to be routed through, but screw onto the frame in the same way? There are some ragley ones on CRC but not sure if these would be universal. And tbh, plastic will do.
If not I'll bodge with O Rings, but thought may as well ask.