Although you can certainly practice and moemorize the rhythms by taping on your leg or playing with one hand on the top of a conga and the other hand on the side, you will not be able to develop your technique this way. This is OK, because it' almost as important to just memorize the parts and get comfortable playing them with the other drums. But, eventually, if you want to really get comfortable, you will need to get your own drum to practice on.
I'm fairly new to Bata myself and have gone through just what you are going through. What i'd recommend is getting a cheap Okonkolo to practice on. Actually the worse the drum the better, because if you can make a crappy drum sound good you will make a good drum sound excellent. I've been told that in Cuba they would make you practice on a drum with the heads tuned down so far that they are almost falling off.
Anyway, try this website:
http://www.interstatemusic.com/12221-To ... -3308.aspxThis is the cheapest that I've seen new bata on line and this is where I got my set of Toca (which are pretty nice once you change the heads).
Hope that this helps.