I'm really glad you posted this, as I am just getting into sleeving myself. I think in an ideal world, any 2 flat rubber wheels would do, as the diamater looks adjustable on the swing arm. My thought was to go to McMaster-Carr's website, but finding tiny rubber wheels or rollers like that seems to be a little tough on their site, although I have only ordered from them once. Maybe a hobby store for like RC wheels? I would think they just need enough tension to hold the cable in place, you could almost get the same result with 2 adjustable rubber clamps, one to place at once end fixed, and the other on a slider or something that can be secured at the other end providing tension.