That number that you gave sounds like a UL file number, not a manufacturer's part number. Look on the inside left or right side wall of the panel box itself. The part number should begin with an "M". I went through this same situation when my panel covers got painted-over too many times and couldn't find replacements.
Surprisingly, a search on e-bay put me in touch with several surplus electrical equipment dealers who were able to get me squared away in a couple of days. There is a major seller of surplus circuit breakers in Los Angeles. The one that helped me was located in Wilmington, NC. Panel covers are a rare find, but I got lucky to not only find one brand new one, but two.