Does anyone make a bedcover like Im looking for?

[lock]

Ive got a short step bed. I want a bed cover that is:

- solid (fiberglass, etc)
- mounts completely flat with the top of the bedsides
- fits inside the bedsides(not one of those that covers the rails)
- opens with struts
- locks
- doesnt leak


Basically I want to be able to securely store stuff in my bed and have a nice looking cover, not one that buldges up. If you know a company that makes ones like this please let me know... url too if available.