No problem if you are driving! We will be driving from Florida to Cal and Az with 200 or so babies again this year. We have drilled some air holes into a large cooler so it takes a while for it to get too warm or too cool. And I could add cool or hot packs to the cooler if needed. Still, don't go out of the car too long to eat, shop, etc. If you have only a couple of snakes, they could go in sacks or deli cups and be removed from the cooler into your handbag or back pack, etc, when going in to a restaurant.
Be sure to put the cooler on something to raise it off the floor of the car as there are hot spots in some areas of the floor. And don't let the sun beat on it either, even when the a/c is on.
You can just buy a cheap styro cooler and punch a few holes in it. If you don't have too many, you might be able to get a styro shipping box for free from a pharmacy, vet clinic, or pet shop that gets tropical fish shipped in. Depends on the size you need.
If you have to ship because you are flying, the easiest way is to pay somebody who is FedEx certified to do it for you.