RPN Calculator with Solver

I would love to have an RPN calculator with a solver feature like the HP 17 B II or HP 19 or the HPCALC.exe works on xp or 32 bit win 7 that came with many HP computers. The equation solver renders the variables from a stored equation as assigned buttons and can solve for any of the variables with the others given values. The calculator can be RPN or conventional (parenthetical equations) for folks who prefer that. The calculator persona can be programmer, scientific, business / finance or possibly custom. The unit conversion feature that is already in toolbox can be integrated into this calculator as well. Some programmable features like functions or routines may be desirable.