I had a look around about this B foot thing.
The B foot flute, is longer than one with a C foot. Its lowest note is B3. This longer foot joint also facilitates some high notes. Whereas the lowest note on most of the student model flutes is C (called C foot), professional flutes have the extended B foot. Some musical pieces, usually in the more advanced or professional category, requires the usage of the B note. Hence, the extended B note allows flutes to be used even for this type of musical pieces.
I dont know if you can buy a different foot piece for your brand of flute, though. A closed hole one seems to be about 500 pounds.
What type of flute have you got?