Buy an Pelican 1120 box you won't regret it. The average plastic bottle used by clinics will be held tight by the foam inserts and will not allow your bottles to tumble around. You can use average size pad locks of any type to lock
These people suggesting cheaper alternatives either don't know any better or have a very small budget. Every time I get my box I say to myself damn that's a good box, other people at the clinic compliment it as well.