In the world of pharmacies, everything is identified using NDC Codes. If you call/goto yours and mention these, then they should be able to tell you whether the medicine is in-stock, can be ordered, or cannot be ordered.
Shire Brandnamed Lialda: NDC Code(s): 54092-476-01https://dailymed.nlm.nih.gov/dailymed/druginfo.cfm?setid=3098a080-be86-4265-9818-7fc4beab77b7
Shire Generic Lialda: NDC Code(s): 54092-100-01https://dailymed.nlm.nih.gov/dailymed/druginfo.cfm?setid=4e3b6325-a5bf-4c47-931c-142c0e4d7c3a
Links include pictures of the labels, both say Shire, one says Lialda, the other just says mesalamine.
There's other generic manufacturers, with different propriatary delayed-release coatings. Zydus, Mylan, Teva Pharmaceuticals, and others.