i buy all my thread, cones and spools now from Connecting Threads- and love them- they have many (types) blends, fiber contents of threads---
i don't know for sure but it seems like only Coats & Clark called their sewing thread- Dual Purpose---that may be why you are not seeing it else where....just the terms- the thread used for many applications is still out there- all the thread companies carry them- they just don't call it that.