Getting the needle off can sometimes be tricky. I've never done it on a TW speedo and don't recall offhand which type of needle attachment ours has but I'll take a look and see what's involved with getting the needle off of one of my junkers when I get home.
I'll bet that one of the youngsters or more tech-savvy oldsters on here could print you out a nice replacement face overlay.
The boy racer crowd does this all the time, creating exact sized white faced, colored or duplicate speedo and gauge overlays with adhesive backings. I wouldn't mind some sort of hi-viz repacement for mine so that I could backlight it with low-wattage red bulbs and lose the glare.