Above pic posted by Stephen on Aussie Africa Twin facebook page.
I've seen a lot of pics and riders saying they've had the OEM heated grip switch block come apart. The button falls out and pretty much the electronics are then useless.
The plastic housing is 2 halves and relies on a tiny plastic clip, it doesn't take much side pressure from your hand while riding to separate the housing.
Before I set off around Australia, I grabbed a bit of 5minute areldite, 2 zip ties and a bit of silastic, a 5 minute fix and 40,000kms later, it's still intact.
Maybe it'll help you too.
Cut the block end off a small zip tie, glue it to the top of the front half (the side facing the rider) wait for it to dry. Pull it over the housing and secure it to the grip wiring loom with another small zip tie. (cut the existing one off)
Only glue the tie to the half facing the rider, this way if for any reason you need to pull it apart, you only have to cut the tie off at the loom.
Just a bead of silicon around the switch, don't jam it in, if it gets under the switch it might make it useless. The bead is flexible and allows the switch to still function, keeps water out and if the block comes apart, there's less chance of the switch being lost in the dirt somewhere.
If you haven't fitted your OE grips yet, you could get a little more 'fancy' and make a thin round disc that goes between the grip and main switch block.
The OE grips aren't cheap, I don't want mine falling apart if I can help it.