Remote entry microswitch repair

It's probably the rubber membrane that is worn out, not the actual switch. If so, then you could transfer the circuit board and transponder chip over to another case. Used keyfobs are available on eBay, and you could just get the cheapest one you can find. Even better, there is a part number listed for just the case at Part Detail I've never heard of anyone actually getting just the case, but it would certainly be worth a try at your local dealer's parts department.

To take apart a keyfob, start by taking it apart like you were going to replace the battery. The hardest part will probably be getting the panel to slide (the latch that holds the mechanical key in also holds the panel in place). I've split the case by inserting a pair of needle nose pliers into the space where the mechanical key goes, and spreading the pliers. The case is stronger than the glue (at least mine was...), so the case should come apart. A couple of dull blades worked around the glue area may help once the case is open enough to fit them in.

Once you've got the cases open, remove the circuit board and transponder (a half inch by eight inch square black chip with no metal connectors on it) from the donor keyfob. Then transfer the similar components from the original keyfob to the donor case. The circuit board is just jam fitted into the case, although there may be some glue holding it as well. Take the donor keyfob apart first to get familiar with the parts.

I put it all back together with ordinary white glue, although others have suggested better glues. Whatever glue you use, just be sure that it is weaker than the case if you ever want to get the case apart again.

As I recall, the UK keyfobs do not have the alarm button found on US keyfobs. But I suspect that you'll find a microswitch on the circuit board where the alarm button goes. The point being that you can probably use any used Prius keyfob that you find, even if it has the alarm button.