There is a 5-6mm allen head bolt that holds the wiring cover on. Just take it out and you will gain access to the last bolt on the filter cover. My 06BA has the oval filter too. I think the round ones you are looking at are pod filters that are to be used with the airbox removed.

06 BA, TOR's, 17T front sprocket, 135/42, needles shimmed, AI removed, drilled airbox, K&N air filter, desnorked, SM seat and risers, drag bars, pro-grips....let's ride!!