Hi P. Lamb, I think what you need is a "single roller". Here are some suppliers: Blaine Window Hardware, 800-678-1919
Hettich America, 800-438-8424 or www.hettichamerica.com
G-U Hardware, 800-927-1097 or www.g-u.com
L.E. Hohnson Products, 219-293-5664 or www.johnsonhardware.com
This is from an article in the August 2000 issue of Old House Journal. It is a good article and may offer some guidance in attaching the door. I found it right AFTER I worked on my three sets of doors.