i had a similar situation as yours last week and asked my lbs if i could replace just the tiny metal cage into which the noodle goes. lbs said no, you've to replace the entire part of the brake that touches the rim. in my case, he bent the cage back into shape. told me since this had to be done only once, not to worry mechanical stress (like bending a paperclip). a few days later i decided to replace that entire part anyway (wanted more clearance for fenders + i don't mess around with brakes). it cost me $25 for deore front brakes. o btw...why did this happen? my front wheel turned all the way back (kind of like a 180) and that twisted the cage.

so no, you cannot replace just the cage you have to replace the whole thing
that'll cost you $25 per brake
you can also just bend the cage back into shape if this is the first time it has happend
i am unreasonably paranoid about brakes so i 'wasted' the 25.