I've had the same problem. And there are lots of things you can do. One thing that I do... which is fun... is take "one-shots" (which are individual "snare" samples or "kick drum" samples) and manually double the snare hits. This is time consuming, but I've had some pretty great results, personally.
You can get one shots from loop cds, drum machines, or even existing cds (it's fun trying to isolate snare hits without any noise), or you can record your own.
However you get your sample, you can easily take that one sample and make it sound like 10 different samples by simply adding effects: compression, reverb, etc. So even if you only have 5 samples, you can make that into 50 by just playing around.
I read somewhere that in the 80s, producers would do something like this to really fatten up their snare sounds. I can't imagine how difficult this was, but with today's recording technology, all you have to do is line up your sample with the drum track by matching the waveform. It's pretty easy, just a little time-consuming. But it's worth it to get the sound you're looking for.