If it isn't compatible with the firmware flash (or by stock ROM), here is an absolutely affordable and truly awesome device that I am beginning to coin the swiss army knife of WAP's and will do what you need:
~ $25 for a wireless N AP... It has TONS of features, some of which you only find on the > $100 models, among them is bridged mode which is what you are looking for. Check out the Customer Reviews tab if you don't believe me on how good this thing is. I think my favorite comment in there is:
``I'm an IT consultant for small businesses. I keep a few of these in my trunk for when a client says "What would it take to get wireless in here". DONE. "I get a bad signal in this end of the office." Repeater mode... DONE. "Can you make this network printer wireless?" Client bridge... DONE. Up-charge them $40 for the unit and they don't even blink at the price. Every one of the units I've installed so far has been rock solid. Runs cool to the touch and just works. It's like a refrigerator... just silently works. If you could install DD-WRT on it I'd use one in my own home. ''