Try any of the online RC and ship modeler hobby shops. They carry most all shapes and sizes of metal stock in brass, aluminum, steel, and often stainless and nickel.
For "V" stock ( if you can't find right angle stock), you may have to use square tube stock and grind off one side. From there you can tap it with a hammer to get the desired V angle.
I make a rivet with an "A" in the center of a red circle. It is made from round tube, V stock, and flat stock. Once I have the V and flat trimmed to the right size, I tack the ends together with CA. This keeps things in place while inserting and drawing up the colored epoxy. I use a piece of plastic tube pushed on the end of the mosaic tube to suck the resin up from a small cup of it. You can do it by mouth, or use a small vacuum pump. Once filled and about 3" of resin is up the tubing, remove the mosaic tube and cap off the end with a rubber cap you can get from the auto parts store. Hang vertically by the tubing to cure for 24 hours. The caps are the type used to cap off vacuum line ports, and come in several sizes.
Any reversible letter can be made this way ( A H I M O T U V W X Y).
Hint:
Thin epoxy is much easier to work with. The bar top and clear coat resins are much thinner.