Brake bung for hydraulic brakes

[Crosstrailer]

I don't think I am imagining this but I am sure there is such a thing as a small plastic bung or stopper which can be inserted into a brake caliper between the brake pads to stop them closing on hydraulic brakes when the wheel & rotor are removed.

Does anyone know what the actual name is and where I could buy them from ? Currently using a makeshift solution

Thanks in advance

 

[djb1971]

Disc brake spacers/wedge

Plenty on eBay but a bit of thick card is cheaper