I wouldn't be surprised if a place like B&H didn't have some in the back somewhere.
Funny you should mention that Tom. Today doing another search with the same terms B&H came up with a couple of hits.

They are listed at over $20+ shipping.

The problem is they list the tripods they fit, but not the size. It may be the last two digits of the numbers; Gitzo D0402.36 Knob Cover for Select Tripods and Gitzo D0402.41 Knob Cover for Select Tripods.

If that is the case, they are likely both too large for my tripod. Tried the chat function but it seemed like it wasn't working.

One of the rings is listed as Special Order. For now my plan is to see if the tape ordered is able to do the job. The heat shrink for fishing rod handles may be acceptable if the tape doesn't work.

jtk