This sounds unethical, and were it a matter of a valuable item with a family cherished history, that would certainly be the case but ...
Don't buy a trolley. Go to lost and found and tell them you lost one. There are a great number of them there, never ever going to be reclaimed, and when you describe yours as metal with wheels and a handle they will very likely give you one to clear it out. They are most likely to be left by people struggling to get on a plane but have no interest in wrestling with the item through TSA or into the overhead or packing it into the suitcase. They may have obtained it from lost and found themselves - the great circle of trolleys. When you are done, leave it at the luggage carousel. It will either go to other adventures or be recycled back to lost and found.
The same applies to umbrellas. Black, folds up small. Or doesn't fold up small. Pick a story and stick with it.