Personal Grocery Carts?

[ieatedyourcooki]

I've been seeing them a lot up in my area lately and they seem convenient, but I'm not sure about a proper procedure regarding them or where to even get one.

Do stores question/allow their use?
Do buses allow them on board?
I saw someone say they got theirs at giant eagle one time, but I have never seen one.

I have a local grocery in walking distance and would like if I could shop more than one bag at a time.
Thank you in advance.