Durabond is a trademark of United States Gypsum. Durabond is a chemically-setting type, powdered joint compound; the 90 you refer to is the set time. Other set times from 20 minutes to several hours are also available. Many companies that make ready-mix, drying-type joint compound also make a setting-type compound similar to Durabond, but if you want to stick with what you've been using, try usg.com for distribution information. You might also try the yellow pages under drywall supplies and/or plastering supplies; most cities of any size have wholesalers that supply these type of products to the drywall and plastering trades. Good luck.