Just a heads up, I've been looking high and low for some new buttons for my fobs and finally found a place in Germany who supply them. Postage was 9 Pounds but the buttons were only 3 quid so I've bought a couple of sets while they are available....
Link here in case it's of use to anyone in 2019
Button for Cobra Hisec Handheld Transmitter 7727 (2x Blue 2x https://www.amazon.co.uk/dp/B006BNR1..._RJaaDbAY6Q52V