No. This is not doable if you're accessing the database at both locations. A mirror or DFS will fail miserably. If you're entering data at both locations, you'll have two different versions of the same database. Reconciling the mirror/DFS will either totally corrupt the database (most likely) or overwrite one copy with the other. Either you will lose all your data, or all the data entered at one of the locations. This will happen every single day. Very, VERY bad idea.
I can only think of three options. First, split up your database (I'm not familiar with fox pro, sorry). If you can create a sub-database for location B that links to the main database at location A, you'll dramatically reduce your network traffic. I don't know if this is possible with your setup.
Second, you can tell your boss he either has to cough up the money for more bandwidth or pay a whole lot more in lost productivity because your workers can't work efficiently with what he's got. (Count up the man-hours lost each month because of the slowdown vs the cost of bandwidth. Couch it in terms of saving him money, not costing him any).
Third, use telnet instead of vpn. With telnet sessions from the remote location all the data resides at location A. Very, very little data passes between the points. The trade-off is the cost of telnet licenses from Microsoft, but that would be less than a new server and OS at location B.