I currently have a Pansat PF-7900U on my dish. I am trying to buy a new one but I can't find a website where I can find it. Does anyone know a good website that sells these LNB's or similar to it?
Tell us more. The part Brian linked above is an excellent replacement for your Pansat http://www.pansatservice.com/pf7900u.htm
if a Standard LNBF will do. For me, I'd prefer Standard over Universal.
Are you adding Ku LNBFs to a BUD?
If you tell us what you're up to, perhaps with a few pictures, maybe some other solution will come to mind.
Did you go to the Pansat page I linked above?
There you can click on Dealers at the top right.
One is an eBay seller.
I didn't explore 'em, but I'll let you.