These are the cooling mats / beds I'm aware of. I think an average price tag of about $50 is what you might expect to see.
Canine Cooler
http://www.fancypaws.com/caninecooler.html
Cool Bed II
http://lucysdoghouse.net/LucysDogHouse/Bedpp12.htm
Cool Bed III
http://www.petronic.com/coolbed.htm
Coldanna Cooling Mat
http://www.roshgo.com/Merchant2/merchant.mvc?page=rc01/CTGY/00904
Miracool Dog Mat
http://www.lovemypetsupply.com/large-cool-heated-dog-beds.html
Canine Cool Pad
http://www.50degree.com/custom/index.cfm?ID=38647
Canine Cooler
http://www.fancypaws.com/caninecooler.html
Cool Bed II
http://lucysdoghouse.net/LucysDogHouse/Bedpp12.htm
Cool Bed III
http://www.petronic.com/coolbed.htm
Coldanna Cooling Mat
http://www.roshgo.com/Merchant2/merchant.mvc?page=rc01/CTGY/00904
Miracool Dog Mat
http://www.lovemypetsupply.com/large-cool-heated-dog-beds.html
Canine Cool Pad
http://www.50degree.com/custom/index.cfm?ID=38647