Micro Mark carries the 2" X 25' roll, listed at $6.85 as of this posting, about $1.64 per square foot.
http://www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=80806
Science kit, however, sells 10cm X 38m roll (about 4" X 125') for $19.95, and 5cm X 75m roll (about 2" X 248') for $21.00. That's $0.48 and $0.51 per square foot, respectively.
http://www.sciencekit.com/category.asp_Q_c_E_431119
I bought the 10cm roll a couple of years ago and it's still going strong. Science kit has lots of other useful goodies, like storage bottles, funnels and other lab equipment.
Gotta logoff and unplug now, the lightning is getting close.
Regards,
Bruce
"You can't have everything--where would you put it?"