Before you buy in bulk online, make sure your snake will eat F/T. If none of the stores near you sell F/T, you can do it yourself. When I was switching my snakes over, first I tried pre-killed. The easiest way I found was just putting the rats in a cooler and then putting some dry-ice in a container with holes and putting that in the cooler with the rats.. they just go to sleep. You can also get a CO2 tank from a paintball gun store and do it that way. Anyway, once your snake will eat P/K, then freeze one or two and next time thaw those out and see if your snake will take them. Make sure you thaw them out slowly (do NOT put in the microwave.. trust me.. LOL), and get them pretty warm, especially around the head. I use a hairdryer. Most of my snakes prefer when I make the rat "walk" past their hides. Then they just come out the opening of the hide and strike, then drag it back inside with them. I think it makes them feel more secure. But it'd be a waste to buy a bunch of frozen rats only to find out that your snake won't eat them.
If Big Cheese is still out, try RodentPro. I buy from them online and their shopping cart tells you how much space is left in the box so you can maximize your order for the shipping you pay.