When I saw a friend's worn out remote car key, I knew that other people must have the same problems, and that somebody must sell replacement parts for repairing the case (fob).
The flexible rubber side of her key was torn and one of the button inserts had fallen out making it difficult to unlock her car doors. Water could get into the electronics and ruin it.
I found the necessary parts kit on Amazon for $3.99, shipping included from China. After repairing the first of her keys without any problems, I tried to order another for her spare key through Amazon, but it was no longer available. I found it on eBay for $1.75, shipping included from Hong Kong. It took the first key 15 days to arrive. I just order the second kit.
To find a replacement for your key fob, copy and paste the link that follows, into your browser, enter your vehicle info, and keep scrolling until you find the right one at the right price.
This is the worn out remote key for a Toyota RAV4.
This is the refurbished key after replacing the fob (case), using only the electronic module from the original. The key blank is molded into the fob, just like the original. All that remains is getting the key cut. All parts fit perfectly, and in my opinion, the new fob is better designed than the original.
First pop the case open by twisting a screwdriver in the slot on the side, just like you do when changing the battery.
The new fob has plastic buttons that fit into compartments in a hard plastic case instead of the flexible rubber buttons that wore out. The rubber gasket (upper center in the picture) holds the buttons in place and provides waterproofing in the completed assembly.
Remove the electronics component from the old key.
That's the switch side of the electronics component showing in this picture.
Insert the new buttons in the holes in the face of the new fob. This was a three function remote that didn't include the trunk release, so that was just an extra part in this case.
Insert the rubber gasket over the assembled button/fob face.
Insert the electronics component into the new fob face.
Snap the front and back together and test the functions on your vehicle to make sure everything is working properly. Have the new blank cut at your favorite store ($2.00 charge for this key at a locksmith shop nearby. Any place that cuts keys could have done it.)