Does anybody have this piece?

You can get it here:
http://www.paascheairbrush.com/store/search.html
and do a search for "HT-1"...it'll be at the bottom of the list.

It's only $4.95 + $6 for shipping, so $10.95 instead of DixieArt's $13.45.

DixieArt shows them for $3.45 but they have a $9.95 shipping on orders under $45.
http://www.dixieart.com/HSet.html

If there are any good art supply stores in your area, you might try them first. That airbrush is a pretty common one so finding parts should not be hard.