Most large stock such as PVC lumber or siding is best purchased from either a home center, a local lumberyard, or a specialty plywood supplier due to the shipping costs.
If you’re lucky, you might have a local sign shop which will order sheets — but probably not if you’re making signs and are seen as a competitor.
It’s used by sign manufacturers, I’ve gotten free scraps from our local signmaker’s shop. Their idea of scrap is more than big enough for CNC projects. It’s also sold on Amazon as composite sign boards
Our sign guy gives tours when he’s not busy, their shop is full of CNC machines, along with letting me occasionally rummage through their scrap pile. Probably gives away my age by saying he went to school with my kids
Hey we all get there if luck enough. The truth is nobody gets out alive in the end. I made a youtube video about my cnc work and at the end I had a dry erasure board that said “Life is Precious Enjoy it and Dont Waste it”. Those are words to live by!
Here is a link to my video. I made this as a presentation to my woodworking club.