Acorn window roller

Hi, about a year ago I purchased from you a sliding window roller and plastic housing for an acorn 2200 series window - your part number was 87-141. part number 87-141 is no longer listed on your website. I am negotiating with the managment company of my building to replace the rollers in all the windows in the building. I may need 500 t0 1000 of these roller assemblies. Are they still avalible? Can they be gotten in these large quantites?

Paul P.