Radio Shack, DigiKey, Mouser, Newark electronics suppliers etc. all carrier
the self-sealing silicone polymer 'rubber' tape.  it is frequently used in
place of heat-shrink tubing and yes, does seem to work well.

there are some 'cheapo' makes of it out there that do not seem to fuse well
to itself.  these are a harder polymer and are next to useless.  look for a
nice soft, squooshy one and i've had good luck with those that are rust colored.

-dan