I get email every week asking where to buy scroll saw ready boards. It's difficult for many scrollers to find thicknesses under 3/4 inch. I'm lucky enough to have the equipment to dimension rough lumber. I still sometimes purchase scroll saw ready boards. It just saves me time even if it's a bit more expensive.
One of my favorite sellers of boards is petersoncustomlumber on ebay. Unfortunately they don't offer a huge selection but what I do get it very good stuff. As I type this they have the following offer up. They have 3 available right now but they will go quick. If you miss this deal add them to your watch list and jump on the next offer. This is for, 8pc of 1/4" thick X 7" X 12" of Black Walnut. I love to cut Walnut on the scroll saw. I have purchased a few of these boxes from them always with great results. The boards are kiln dried and sanded both sides. They offer free shipping inside the continental US. I think they also ship international but the cost may be steep for shipping. This is not a paid ad. It's just a seller I use and respect. Check them out. Just don't buy everything before I get a chance:)