I have a rodless cylinder on the SMW barfeeder. The seals are completely shot where the cable enters the ends of the cylinder. The price for the seals from "Them" is around $400. For a few small O- ring sized seals. That works out to about $2,000 an ounce, more than gold.
The (current) cable is about 4mm diameter. The bore for the seals is12mm. The seals are about 12mm OD, 4mm ID, and 4.5mm thick. This is similar to a U-cup design.
Strike out with McMaster, MSC, and local hydraulics houses. I don't see any seals that small.
Smallest possible O-ring size would be a dash 007 or dash 105, if I were to make a new housing, and use a different size cable. Only possible size Quattro ring is a dash 007, again more re-design, and I'm not sure a quattro ring wil seal on the ID to an aircraft type cable.