Decoy for the Win?
Safes should be just that, safe. So, purchasing a small, portable safe, defeats the purpose. If you must buy a small safe, you can use that one as a decoy to throw any potential robber off the trail of your actual valuables. If the safe is small enough, they just might take the whole of it instead of trying to open it on the spot.
Do not keep anything of value in it, just things that you don’t mind having stolen. Keep the safe locked, nonetheless, and make sure there is something in there. You want to make them feel like they’ve hit the jackpot. I suggest filling it with something like papers and old gift cards – so they assume it is filled with credit cards.