I agree with Patrick amd Bernica. Rent a garage and a couple of those portable storage pods and get the garage floor finish you want. Don't settle.
Not too long ago, I bought and installed 4'x6'x3/4" horse stall mats, not for my garage though, which can obviously withstand a huge beating. And they're about $40-50 per mat. But I'm not sure how they would do with casters supporting heavy loads. And they're not very pretty. However, they're excellent, last forever and do the job that they were intended to do for me.
Rubber Mat, Black, 4 ft. x 6 ft. x 3/4 in. - For Life Out Here