Backyard Ice Rink Questions?

I know it is only summer, but i want to start planning for a backyard ice rink in the winter. My first question is where can i get a plastic tarp/liner because i don't want to wait for the snow which most likely will not fall until january? I have been on http://www.nicerink.com/liners/ and they have a good selection but it seems somewhat expensive. Also, what would be a good size to play small hockey games on?( I was thinking around 85 feet x 27 feet). My yard is about 92 ft long and 27 ft wide (with about 6 additional feet including a concrete patio). Would it be bad idea to put some of the rink across the patio? Any tips/comments would be appreciated