Bose has good customer support, give them a call, they'll probably take care of it for you. Unless it's really old and out of warranty.
Is it the bass module or one of the satellites? I think the grills pop off on the satellites and you can get the speaker out that way. Don't know where you can find replacements though; Bose tends to use their own proprietary drivers.
Here's a disassembly video I found: