I've tried to model one of those v-shaped phone holders in Fusion (and recorded the session, but didn't upload it yet … or probably ever, because it's too long and chaotic tbh 😐)

• foldable
• magnetic (so it stays together on your key chain)
• lightweight
• added two magnet variants: 6x3 mm and 4x2 mm

I've glued in 6x3 mm magnets (because that's what I've had), but feel free to use smaller diameter ones - just make sure they are flush to the surface if the thickness does not match the depth of the hole.

Have fun 😁

Edit:

I just noticed that my approach looks a lot like the design from Pork3d (I saw it under “Related Models”).

Which is ... kind of fascinating, I guess? What a coincidence, we somehow approached the problem in a very similar way. 🙃