Around here only Woodworkers carries it. The hardware & big box stores carry birch plywood but not Baltic Birch.
You want B/BB rated ply. That’s very consistent and should not have glue, voids or other issues with it’s construction that will impact lasering.
They call it Baltic Birch, but it looks nothing like the stuff I got from Amazon. (And I’m too new to this to be able to judge it yet.)
I can’t speak as to TX but what the home stores sell around here is NOT the baltic birch I get from specialty sellers.
Well, I’m planning to use up the supply of it that I got on prototyping and for making jigs for other stuff. (Then I’ll need to find another source. Hoping we eventually get some 1/4" PG.)
I don’t see how you can complain when plywood is warped. That is just the nature of it. It might be flat when dispatched but at a different humidity level it will be warped because of the differential expansion of layers with different grain orientations. I hate the stuff.
Gee, the 3 shipments I got were all slab flat. That picture of the warped stack shocked me. Like @rpegg I store them stacked with a weight on top. The only issue I have occasionally had is the masking would bubble just slightly in a couple of spots. I just roll it back down.
I’m pretty sure that is a result of humidity differential between Seattle and the high plains of Colorado. That’s from one extreme to another.
I would speculate that that shipment was subjected to unusual conditions in transit, but just a guess based on my limited experience with 
Yeah, I definitely didn’t expect perfection, plywood is plywood, but that was worse than I expected. I think I’ll stick to hardwoods or only buying what I can see first. Or acrylic.
Remember that you’ll want to use plywood if you’re going to do living hinges. Solids don’t work nearly as well (if at all) due to the uni-directional grain (tends to split).
Good point, also if you don’t want wood grain to distract from your engrave.