For the last couple years I've been using Uline's insulated shippers. It's a two-piece styro cooler insert inside the cardboard box. I pay a bit more for them than I would for the industry standard, but for me, the peace of mind is well worth the extra expense. I never had issue with the pack flat red label boxes, just wanted something more solid. Personal preference.
I buy my bags, deli cups, and heat packs from TSK supplies.
SYR is basically just a third party shipper. You package the snake up at your location using your proper shipping materials and following their guidelines, and purchase the shipping label for it through their website, which you then print out at home and place on your box. Drop off at your nearest hub or other drop-point as usual.