88 80Q brake fluid reservoir cap

[Dr. Cory Brayton]

I opened my hood to check oil for 1st time since my car returned from having
AC compressor etc redone AGAIN a few weeks ago & noticed that cap to brake
fluid reservoir was cracked -- in a circle, as if it had been cranked down
too hard -- dealer/service place says that they don't have part & can't find
it in their catalogs -- of course they claim no responsibility & I know that
would be too much to expect, tho I've never open or shut the reservoir &
they are the only place to have worked on it (5 times?) in last 6 months &
they changed brake fluid 2 or 3 visits/months ago

Any ideas where to get the part?

Is it really not available?

How bad is it to run car with the crack?  levels look OK

Thanks again

Cory B
88 80 Q
Houston TX