Make sure you rotate the retainer clip on it's side
Materials:
(8) 10x10x10 N35 (Neodidlium) magnets (they're more like 9.5mm apparently)
OR: (4) 20x10x10 N35
Notes:
Make sure the inside magnets are coated to keep them from rusting! (e.g.: epoxy dip)
The wall that interfaces with your sump is intentionally super thin, it may even be a bit wavy depending on your print, but as long as it keeps the magnet in you should be golden.
Make super sure you align the magnet poles correctly when populating the magnets for each part.
Fusion 360: https://a360.co/3iQ1UWi - there are parameters that should make it easy to change dimensions if you need something a bit longer/wider/etc.