Am I missing something here? I mean I have the crank arm here on the bike in front of me and it definitely does not seem to have a square taper. Does Truvativ produce one off sort of cranks for certain bike manufacturers (my bike is a store bough 06 Specialized Rockhopper Comp)? Seems a bit silly.
You can use a standard crank removal tool if it is a square tapper. Go to your local bike shop, we always have used and new replacement left crank arms. If it's the powerspline demand a new crank because they suck. I have never seen more problems with crank arms falling off when it comes to Truvativ.