What does everyone do for bedding at big shows where stalls are concrete and mats aren’t available to rent? Is there any mat alternatives that are less pricey and somewhat easy to travel with? 

I have mats I bought at Lowes....the little smaller ones that come in primary colors or grey.  Certainly not heavy duty, but I've used them probably two dozen times in stalls at shows on concrete when rental mats were not available.  They are still in good shape!  Of course, I washed/cleaned them after each use and stored them.  I also use them in the aisle-way at shows for an area to stand my horses while grooming/saddling.  It's pretty amazing how well they have held up.  They are small and light -- so super easy for me to handle. 

I bought these

Marcy High Density Non-Slip 24 sq... https://www.amazon.com/dp/B005CAIXOS?ref=ppx_pop_mob_ap_share

They are about 3/4” thick and seem pretty tough.  I only have to use them a couple times a year, but they’re holding up.  I haven’t taped them in the past and they’ve stayed connected pretty well but my guys are pretty chill.  If I had a pacer I’d probably duct tape them.  I have one gelding who loves to lay down but usually won’t if he’s on concrete and he does when he’s on these mats.

The stall feels nice and padded when I walk in it anyway.

Was one set enough? Or did you buy multiple sets? 

Put down 4 or 5 bags of pelleted bedding and then fluffy flaked bedding on top of that.  The pelleted bedding is heavy and will pack on the floor and stay under the shavings and keep the horses up off the concrete. 

I would also like to know. A 10x10 stall is 100 square feet so I'm assuming you would need four sets of these since one is 24 square feet. But I've never been good at math so someone help me out lol.

This definitely works, however, some facilities ban pellets.  

Not sure if that would work. I have the mighty lite mats that interlock. 9 mats that will cover 10x10'. But the thing I found at a place we go to a lot is that the stalls are not quit 10x10'..... The corner posts are in the way...  So I can't use all 9 mats. Most of the time I use 4 or 6. When I use 6 they always stick out in the aisle a couple of inches. 

So I just use 4 mats, and put them in the middle of the stall. Then add pellets and shavings on top. My boy is a walker, he will move all his shavings to the outside of the stall no matter how often I spread them back out. 

Of course it might not be that way in other places, but it is something to keep an eye on.

ETA a drawing to show the corner posts