You're looking for "Fairly lightweight" and "around $60". Are you into DIY?
8 yards of 60" silnylon @ $6/yard = about $50. (Look through the archives for suppliers. I can personally vouch for Ed Speer.) Sew yourself a 10'x12' tarp that won't weigh a lot.
- Save yourself weight and cost by doing a regular hem rather than grosgrain edging.
- You can use 3/4" polyester webbing for tieout loops, might cost you another $5.
You can easily customize a decent, tarp for your liking for a small investment in time.