Lockable cart

Hey guys I have quite a bit of stuff to carry around, like dog food and toys, and my duffel bag which is pretty heavy. As well as some medication etc and a handheld computer I really don't want to get snatched if I go into a gym etc to take a shower.

I'm hoping to find a lockable cart, like a gorilla wagon or one of those mesh shopping carts I see a lot of people using. I just can't find one where I can lock the cargo compartment shut. That would be ideal I think, so I can worry less about my things disappearing.

Please let me know if you know of something like what I'm looking for, thank you. What do you guys use to carry your items? I'd like something I can feel secure locking to a post etc and maybe leaving for an hour without fear of it being stolen.