If it's made from ABS, it can be welded using acetone, or you can make gap-filling acetone / abs chip slurry (about 60/40 acetone to abs). Acetone-welded ABS is as strong as the original, gap-fill slurry is slightly weaker. If you go for the latter, you'll obviously want chips of ABS that are the same colour as the victim board.
Given that we're talking about a $1200 keyboard, you'll "probably" want to practice on something cheaper and more disposable first.
Acetone chips can be made by running (for example) bits of printer through a planer.
(edit) "ABS chips can be made", obviously, not acetone. You could probably use custom ABS keycaps, too.