Steve-

For wool felt stock in thickness up to 1.0" go to McMaster-Carr

Use the search feature on the left side of the screen, type 'Felt' and let it rip.
From there go to 'sheet and strips' from the big part of the screen, and from there go to plain backed, you'll have more choices and will be able to choose the quality and quantity.

The price is about as good as I've seen, and there is a great selection. Some grades of wool felt are more expensive than others, so shop around in the menus there. I tend to go for pure, relatively cheap firm gray wool.
It's been a while since I've ordered, so browse away and see if the prices compare to what you're used to.
I like to buy it in this way, as a pad of felt packs easily with the rifle and is a versatile piece of material for all sorts of things in the field.

--Tinker