However, if you integrate the databases into one file, even with no data, and then upsize, SQL will recreate your relationships etc. Then you can upload the data using DTS from various sources.
The problem with moving only one is that you will need to move the database tables, then use the Link Table Manager to point to their new locations. Access may rename them dbo_tblName, in which case all your queries are hosed, etc.
I would consolidate and upsize. You may need to install DSN's on all your user's PCs, but you can launch a script to install the DSN when they open the database.