Depends on the type, make, and size of the blade. Also the type of material you are interested in. Whatcha got? Whatcha interested in? Ebay has an assortment.. I just got a decent deal on two pair of wood blanks. In the past, I have made my own scales from horn.
There’s some on eBay, etsy, Maggards razors, Larry at the whipped dog,or you can make them fairly easily out of wood or there’s a lot of other material options.Another place you can look is knife making material suppliers.
Some Scales to Consider.. https://www.ebay.com/itm/vintage-He...564765?hash=item1aaf70f31d:g:RqQAAOSwWUJf0n-D And.. https://www.ebay.com/itm/Straight-R...703834?hash=item4227de075a:g:f4sAAOSwfS1f8kpf Billy..
It might be easier, and cheaper to find an FWE razor on ebay, that has a damaged blade, and swap out the scales. I have done that with several razors. But, if you are intent on using the brass, I would probably buy Acrylic Blanks that are the color you want, then shape them. Or make your own out of resin. Both are very labor intensive.