Where to get rubber tubing for guitar hangers?

I have several guitar wall hanger brackets installed in my music
room. Typical things, they look similar to these:

<http://accessories.musiciansfriend.com/product/Musicians-Gear-Metal-Guitar-Wall-Hanger?sku=542099>

The tubing (neoprene, I assume) that pads the fork has split on a
couple of them. Any idea where to get more of the tubing? All I see
on the 'net are industrial suppliers who sell large quantities for
$50 - $100. I need, like, about 12". I was in Home Depot a few days
ago and I didn't see anything like this, although I didn't have time
to scope out the entire store. What kind of place would carry
something like this? Plumbing supplies? I don't know what it's
commonly used for.
.

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