A flag on the floor is almost never a flag problem. Work down from the pole.

Indoors: a cross base sized to the height

Wide enough to stand the flag, narrow enough not to trip anyone in an aisle.

No ballast needed, which also means nothing heavy to transport.

Grass: spike it

A screw-in or drive-in ground spike is the cheapest and most secure anchor available, and it disappears.

If the ground takes a spike, take the spike.

Hard standing: mass, stated as a number

Tarmac and paving cannot be spiked, so the only thing holding the flag up is weight.

Ask for the figure. ‘Weighted’ is not a specification.

The spares that actually go missing

The base spigot, the top pole section and the carry bag.

All three strand a kit, and all three cost a fraction of replacing it.