If you don't want a live mouse to use for scenting the rats, then go to the petstore and ask them for a little bag of their stinkiest, dirtiest mouse bedding. Do a little shake-n-bake with your rat in that stuff and see if it helps.

No matter what you try...don't keep trying new things every day or two. If your snake refuses a meal for whatever reason...give it a week (or whatever your usual feeding schedule is) or so before trying again. To offer food every couple of days is usually counter-productive and the snake's refusal could have nothing to do with the type of prey.

Good luck!