HiIt happens ...
Holding the crack together with finger/thumb, gently wiggle the handle until it comes away from the head. From memory, it fits onto a stub about a centimetre long.
With the handle off the head, use a cocktail stick to dot some epoxy into the inside of the handle down the top hole taking a lot of care not to get any on the very top or outside. Just a little will do! Push the handle back onto the stub. This will do two things: first, it'll glue the handle back on; second, some of the epoxy will be forced into the crack from the back which will give it some strength without it looking too ugly from the outside. Secure with a rubber band until dry which will hopefully help keep the crack closed up a bit.
When pushing back on, ensure it's not pressed up too high that you can't operate the twist mechanism.
Is that an offer for a 1 off?That should do the job.
I'd probably throw the handle away when/if my one splits, and make up a nice wooden handle (something Joris looking)..
But some folks don't have the time or the tools to faff about (unlike me).
Your repair should last a few+ more years though.
They are not a bad wee razor are they?
I have one as my travel razor.