I bought a car mount with 3 large (9cm) suction cups from AliExpress and it arrived today. It provides very strong suction even on my table which isn't very smooth. I will definitely try it with a Gear 360 on a car. I'd say it's strong enough to carry a camera up to 1kg.
Here is the link to the mount which I paid 14.61€ for: https://www.aliexpress.com/item/x/32498786954.htmlIt arrived in Germany 20 days after I ordered.And here's a photo I took:
The price / sturdiness ratio of the mount looks excellent! Thanks for the tip, I just ordered one as well.
Let me know your opinion on this mount once it arrives. The weak point of the mount appears to be the plastic bridge holding the three suction cups together, but it's not too shabby.