$40 for a can of Freon? I think /not/.

There is a product called DURACOOL which is sold in Canada. You can buy it for $8 a can shipped to the US.
http://www.duracool.com/
The down side is that it's PROPANE (yeah, like you heat the house with) and JUST a bit flammable! Other than that, it's a direct replacement for R12 and every system i've used it in (old uncoverted r-12s without even vacuuming them) it will freeze you out in minutes. VERY good cooling!