You might find some clear tubing at an auto parts store. They should have some various diameters of tubing that is clear. Some of the tubing might be a bit thick but you'll have to see what is available at the store. Also, consider how you'll transition from the tubing to the connectors - shrink tube?
It'll depend on the connectors we end up using. Since he wants two straight mini to mini connectors, it allows me more breathing room at the transition point. I have adhesive heatshrink that is very easy to work with and would offer a good result. I'll likely try and find tubing with a diameter that fits into the tubing so I can heatshrink it to the actual connector inside as well as outside.
One Head-fier asked if I could make him an interconnect. We talked about the style he wants. While I've never done one in the style he's asking, I'm always down to try and find a solution. Think I'm going to check out some vinyl tubing. Hit up Home Depot and maybe the pet store aquarium section for different tubing options.
My only real concern is flexibility. I just thought I'd ask here first. Maybe someone could save me the few hours of searching, trial and error.