The alternative is to have a safety deposit box available for guest use at the front desk. These are similar to what you might find in the vault at a bank. A unit similar to the one depicted below will cost about $500.00 for 5 boxes.
These types of units come with two types of keys. A master key, held by a staff member, and the unique box key handed out to the guest. Both keys are needed to open the box. It's important to note to the guest that if the safe key you provide them is lost, it can't be replaced and access to the safe will be nearly impossible.
These units also come with bond boxes for each safe. This way guests can be discreet. Some guests may opt to sign out the bond box and take it up to their room, place their valuables in it, and then return it to the office in exchange for the key.
Another added benefit to having the safety deposit boxes in a central location is that many properties typically have security cameras. If there were to be an incident, it will be caught on camera.
A good rule of thumb is to have 1 box for every 10-20 guest rooms. These do not get used very frequently but I would have a minimum of 2-3. This is particularly true if you want to use one of the boxes for personal use.