For what it's worth, I found a place that advertises that they rebuild antique picture tubes (they say the Philco Predica is the most common picture tube they rebuild).
The URL is:
http://www.hawkeyepicturetube.com/
Hawk-Eye Picture Tube Mfg., Inc.
724 Scott Avenue, Des Moines, IA. 50309/5052
Phone # 515/288-8567 • Fax # 515/288-8568
I haven't inquired yet, but I probably will E-mail them soon and inquire about whether they do 50s era color picture tubes like this Motorola.
Joe