I saw this auction today: http://cgi.ebay.de/NEU-Reflexspiegel...-/320543055904
I had the mirror in my 4x4 Rolleiflex and one from a Rolleicord resilvered (plus a protective SiO2 coating) maybe ten years ago. The small Rolleiflex had a special thin mirror, so I wanted to use the original. Maybe there are companies that resilver telescope mirrors in Portugal or Spain? They should be able to do it.
Here's an american optical coating company: http://www.clausing.com