There are other "what can you use (or what do I use) for tail stands" threads so you might want to check for info in those.
And yeah, when the question comes up we do need to know what specific light is in question so someone can suggest what works for them,
Yet another reason there needs to be a database of dimensions for tailcaps and bezels for lights that includes stuff like OTC medicine bottles, different plastic caps, and so on. If we had interior and exterior measurements of those and of lights it would be a lot easier to rig up diffusers, filters, tail stands, and candle mode gizmos.
On the other hand some folks just use Silly Putty or stuff like it if the light is small enough. It's good to get creative but it's easier if someone else has been there first.