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I killed several birds with one stone when I went to Harbour Freight a couple months ago.
http://straightrazorpalace.com/misce...kit-combo.html
Its only a few bucks more than that masterlock item, and it is multi-role. The cons: neither the locks on it, or the case housing itself is nearly as rugged & durable as the ML case thingy. The key, and thus the lock tumblers are very simple, to say the least.
I point out my HF find because I believe it will, with slight overkill, fill your need. It will organize & lock away both razors, as well as any other shaving related things that would be unpleasant for her to ingest.
The lock would be easy to pick for anybody with a brain for it, age 9+. Even then, it would be challenging for the more "cat burglar" like clepto-kiddie-in-training.
But by the time she can pick the simple lock, she should fully be able to grasp the concept "don't touch! It can hirt you!"
Hope this helps.