as far as I know you can only get them online...
www.eztest.com or
www.dancesafe.org.
all it will tell you is if your pill/crystal contains MDMA or not. some of the reagents will give color changes for other things too so you may be able to tell if your pill is adulterated with amp/meth, DXM and others.
the most common adulterant these days are piperazines and the kit can't test for those. but if you get a pill and test it and there is no reaction at all, its a pretty good guess that you got piped. since they give no reaction, you may find a pill that is a mix of pipes and MDMA and only get a reaction for the MDMA
But the kits are the only weapon we have against the couterfiters so even though its has flaus, its better than being unarmed.