Try this:

With the car on the lift, use poster board, scissors and tape to template the sump you want. Mark the pan with a sharpie to define exactly how the cardboard sump attatches, labeling your new sump with front and back.

When you're done, pull the pan and take it to a fabrication shop. They'll use the poster board to template some steel and weld it together, after cutting the bottom out of course.

No it won't be cheap, but it will be exactly what you want.