Truth is, whatever the item, if it sells loads, they would never allow themselves to run out of them or they would be at serious risk of losing revenue.

Example: Any phone shop you go or official Apple retailers cannot afford to run out of iPhones and iPads otherwise the punter will veer off to the shop on the opposite site of the road and buy them there.

For all other item which there is no major demand, to them is a matter of order and supply only, no one will risk stocking things that do not sell volumes.