Go into a copy of srb2.srb using XWE, and tell it to only show the GFX. Then, try copying the lumps for the letters, numbers, and symbols (all of them, there are a few at the end too, and there's two styles of both numbers and some extra symbols). You can then work from there.
Oh yeah, and before I forget, text on the menus won't get highlighted except in the areas that use shades white or gray.