Yes, I made my own. I picked up the headliner material at Joann Fabrics. For the backer board, I used formica laminate I peeled off my old kitchen countertop since I was remodeling at the time. It is very rigid and strong yet very light. For a template, I used cardboard and cut it to fit just inside of the plastic trim around the t-top opening, and to tuck under the trim on the t-top itself. Almost looks factory if I say so myself.
My "custom made" covers came with the car, but they were just cardboard painted the color of the interior. I'm cheap too but they worked fine for the previous owner and me too. I would just trim some cardboard, paint it and use that.