I just invented my own claw caps using denture adhesive [watch for my new post soon, with photos]. It's like a dentist making a mold for a crown. Clean the paw thoroughly. Remove all fur from the toe with good scissors. Heat the plastic in hot water -- ceramic cup, handle with metal spoon (it sticks to any plastic) -- until it turns clear and pliable. As it cools and hardens, it turns white. It remains pliable at temperatures below burning hot, so you have time to work with it. Use a glob about the size of a pea. Mold it onto the claw, hold until white and hard (a minute or so). Mark the top side with a magic marker or Sharpie pen, else it's really hard to get it back on right. Pull it off (do not let go), have your assistant (it's a 3-hand job) carefully place a drop or two of super glue into the cavity, then cap the claw and hold until the glue sets.
Use quick-setting super glue.
Practice on pencil tips first.
I did not use denture adhesive. I have a plastic splint left over from a hand surgery, same stuff. [Anybody know where to buy this stuff? Amazingly useful.] I cut off small pieces and heat in water in the microwave.
Ensure that your caps are not too wide or too big; you must avoid distorting the posture of the foot. The caps must not spread the toes apart.
Super glue is spilly and bonds skin instantly. Be careful. Assistant recommended.
Super glue was developed for medical uses -- closing wounds, replacing sutures -- but the original stuff (now sold in hardware stores) is too inflammatory/irritating. It's been reformulated. The veterinary stuff is called Vet-Bond. DO NOT USE SUPER GLUE FOR CLOSING WOUNDS. It's extremely hard for the E.R. people to clean out. I used super glue here because it's just plastic-to-claw, not an open wound.
Good small precision cutting tools (maybe a good nail clipper) might be handy for removing any rough edges.
Inspect your work closely and often for any unexpected problems.
Gwynnie has DM, no cart yet, but she's scraping her hind feet badly and wearing the claws down to the quick on pavement. So far, this seems to be working.
To be continued.