my 08 prius smart key lost the cover for the lock and horn activation buttons. finally found a replacement cover from Polmex good instructions warm with hair dryer to remove old 3 button cover clean recessed areas and then press fit replacement 3 button cover into place . replacement cover is not painted but has embossed symbols for lock, unlock and horn.
once installed no longer worried about the inner electronics being destroyed.
replacement pad was received in short order and reasonably priced purchased on ebay.au section <$20.00 you can review all products by going to Polmex
this is better than replacing the entire case from another smart key.