If it is older can you just put a bit of glue to hold it?
but if newer I wouldn't try that.

do things flop around or wiggle because of this piece missing?
if not and if you don't carry it around a lot it should be OK, but I'm not a expert with laptops at all.
I did google "HP laptop parts" -you might find what you need on one of the links
http://www.google.com/search?hl=en&q...=Google+Search