Every size MDF base you could ever need! If your size isn't listed message me. I'll charge you for the closest size rounding up and it won't be a problem for me to cut them for you.
I use 3mm thick MDF purchased from Craft Closet. This MDF is slightly more expensive than most of the stuff sold on eBay and I believe it is better quality apposed MDF made in China and shipped over here.
I can do bulk orders if you need a ton, just let me know.
I run a small 3d printing/laser cutting business with my two young children. It's gives us a bit of hobby money. Feel free to message us is your looking for something weird, we may be able to help you out.