There is some information in the
datasheet that can be easily research.
operating point typically is 90 Gauss, so a magnet like
this one will suffice between 5 and 10mm.
Unfortunately you cant get this information from eBay, especially any from China. But in general small one should work well.
To get the Gauss reading -
https://www.supermagnete.de/eng/faq/...x-gauss-magnet