Got mine from http://www.reptilesexpress.com/ since it seemed a lot cheaper than SYR (Ship Your Reptiles). SYR may have a discount coupon, I know they do for shipping your reptile but I don't know about buying supplies
At ShipYourReptiles we offer shipping supplies that meet the FedEx requirements for packaging and shipping live reptiles. FedEx requires at least 3/4" insulation for your box. A few companies also offer 1/2" insulation for a few dollars less, but it does not meet the requirement, and it offers less protection from a thermal AND structural aspect.