Is it specific to the CBR600F? If not, what other bikes share it?

Where can I buy one?

 

http://www.hondaparts-direct.com for brand new.

http://www.ebay.com for used.

 

You could always rebuild the one you have, and If its the fluid check window that went bad (typical on hondas) I just plug them with a piece of plastic cut to fit and then epoxy it to create a seal. You will want to scuff the edges up for a good bond though. Good Luck