I work for one such place it's
Bornmann Mfg. Co.
3731 Old York Rd.
Philadelphia, PA 19140 (215) 228-5826
Most of the other places in Philly buy them from here including Home Design Shop, SMK Enterprises, Kessler Supply, Connells Windows and Blinds, and Fernrock Hardware just to name a few tell them John told you about this in this post.