This may apply to models other than the i30, so I am posting it here...
I think I might have spilt diesel or some other unfriendly substance over my i30 key fob, so the plastic(?) or rubber(?) bit hardened, perished and fell apart.
Instead of replacing the entire key fob for half a bazillion dollars, or swapping over all the components (as per these instructions at
Hyundai Flip Key Shell Replacement - YouTube) I decided to purchase a shell from eBay
Hyundai I20 I30 Flip KEY Remote Replacment Blank Shell Central Locking | eBay for AUD$11.45 and merely swap the button-pressing-thingo (herein referred to as the ‘BPT’).
It appears the BPT is not glued so I was able to (gently) prise it off the new fob and place on the old fob (below right).
I was worried it would be inferior material and/or the white paint would disappear. However, after nearly 2 months the only issue has been the BPT suddenly decides to start lifting off and detaching from the fob. To solve that I decided to use a few dabs of silicon to ‘glue’ the BPT and the fob together. All seems to be working okay. Not bad for $12 and 10 minutes work!