Posting a similar thread myself awhile back, I was recommended Smart Loops.
It's a cd with .wav files of 1-2 sec drum beats and fills that you lay out sequentially as necessary. The audio quality is great, there's lots of pre-set loops of various styles, and all the individual hits should you ever want to create your own from scratch or add on top of the loops.
Working with it would limit you to playing with or near your pc though, unless you burned a cd of your finished beats. And the samples come in rates of 75 and 100 bpm...to change these further require whatever audio program of choice to speed up/slow down without drastically changing the integrity of the sound.

Otherwise perhaps just a simple drum machine that could be in your signal chain to your amp is what you need. They've gotten pretty cheap and even many effects processors like Digitech RP pedals come with practice loops that are really good for practicing purposes.