There's really no need to send a slab to china.
The material used is most likely polycarbonate, and that can be printed in a 3d printer. Most hobby machines probably can't achieve the quality needed to produce a nice clear item, but the professional machines can.
Check out some of the items shown on this page and ask yourself how hard it would be to make a slab. Or a mold to produce some slabs if you had an injection molding machine. (Or even a press that can both heat and press at the same time)
https://www.makexyz.com/printer/medspark
And he charges just $1.75/ cubic centimeter.
The printer he uses can be had for about 20,000 used, sometimes less.
Steve B