I have a place close by called
https://www.metalsupermarkets.com/ that sells their scraps pretty cheap. I paid about $25 for four square of steel that are about 1/8th of an inch thick, and I would put those under my jack stands to keep from damaging the tiles.
With that said, I would never install another modular floor, but that's just me. My father installed one and only parks cars on it, and it looks great after ten years. I installed one, and in five years, it was a disaster because I work on cars in my garage.