Thanks again, those would be ideal. 5mm wide means they will fit just over the buttons and 9mm tall will poke out the top of the enclosure just great. These are the first I've seen that would work - awesome!
In other good news is Digi-Key do ship to Australia, but that's where it comes unstuck. It's $34 for delivery (unless I buy $200+ which is a lot of caps !) so my little $2.56 (even when I added more in for extras!) soon blows out. I've setup an eBay alert, but hopefully I'll find someone locally who stocks them to avoid such a major delivery hit.
Thanks again, Geoff