Luckily 5TP4's are fairly common, don't think I'd waste the money on rebuilding one at this time (maybe in the next lifetime). I think I have 6-8 of them around here.
Clausing is a bit more expensive than this place Spectrum Coatings in FL
(
http://www.spectrum-coatings.com/)
I paid around $225 for my 901 mirror about 4 years ago. I just brushed some flat black paint for the center.
Chuck