I use a plunger style detachable keyring connector* for the ignition key and the other associated keys I use for the bike (lock keys, top box key etc.).
On the bike, the ignition key is separated from the other keys that then go safely in a zip pocket. Off the bike it means I can keep them all together.
*
Like this (random Amazon search result - better quality or different size etc. may be available elsewhere.) Use the female end for the ignition key and wrap some tape around it to minimise yoke scratching.