Sure I just installed a 72″ 60″ shower pan 4 weeks ago. All you do is look in the yellow pages under “Licensed Master Plumber” and have this craftman custom make one for you using 4 PSF sheet lead with the drain outlet installed any place your little heart desires.
One piece shower pans are mass produced to certains standards, the drain location being one of them. There would be no economic advantage to mass producing one with a special drain location. The best you could do would be to have an imitation marble pan constructed. This will normally be in several pieces and you will need the same safety liner that a tile shower uses.