Here’s an example of the cheap +1 Cokin P diopter in the cinetactics Matteblox. It is a velcro mounting system, so the adapter is mounted in velcro and can firmly attach close to the lens. There is no possible chance of this falling out accidentally.
Notes & experiments
How I mount diopters to the LA7200.
Edited from the Eyepatch archive. Technical observations and credits reflect the original material; old availability and prices are historical.