When we were travelling in our T4 Westies we had a small safe under the bed and bolted through the floor. This was for cash/credit cards and passports. We also hid bank notes in the van places. I’m sure there are still some there with new owners as we forgot where we put them
Have a think about what you could hide up in the poptop for instance. A laptop aliased as a pillow. We have a small box buried in one place on the bus which was big enough for passports and small electronics. And a collection of blankets, cushions and junk that we use to break up the outline of bags containing valuables.