find
can be a bit slow because it enumerates every directory recursively from the root you specified, but it let’s you do a lot more than just search by name. locate
is available on most distros and give fast results, albiet from when the index was last rebuilt (usually nightly). They both have the vital property that they output a list of files to stdout for further processing.
I think you’re going to struggle to find something that can carry 200lb and be collapsible. Most carts seem to either be for much less than that, or much more. I found several that looked a bit like what you may want by searching for ‘vendor cart’.
You may well be better off building/comissioning something to your spec though as a lot of the bigger carts are designed to be food stalls when stationary, so they’re probably unnecesarily heavy. I think you’d be able to make something along the lines of what you wanted with parts from your local DIY store.