How about a tarp
http://www.jacksrbetter.com/index_files/Products%20List_files/8x8%20SilNyl%20Tarp.htm
$50
and
http://www.ula-equipment.com/circuit.htm
$175

ok so I'm $25 over, but this is great gear.

Depending on where you go and what pad you choose you may need a bivy bag or a ground sheet to go with the tarp.