It's not an instant option, but maybe open a separate current account to use for work stuff? I did this years ago and it's a lot easier to keep track of expenses if they're all on the same card/bank statement (and you can pay yourself at the end of the month or whatever, so your personal bank statements look better and more organised).
I know it's a pain if you're busy, but I would try and set a bit of time aside to bank regularly - sitting on a load of cash in a hotel room is a magnet for robbers even if you're stashing it well
. I used to get the cleaners in first thing and go out to do it then (and pick up stuff for lunch and so on)