R406A and R409A contain R22 which is bad for the hoses and seals designed for R12. I searched the web and found many alternative refrigerants. Some of them available in Canada cannot be sold in US.
Here is one place you can start surfing the internet for A/C information: www.hdair.com/links.htm
Without knowing how well other refrigerants work, R134A is my next choice beside R12 at this time.