If you have an iPhone with MagSafe, you can search for "compact iPhone mount" on Amazon and you will find a number of small mounts that work well. I can't find the one we got but it was quite similar to this (apologies for the ridiculously long URL -- Swedish site but German site should have similar products)
https://www.amazon.se/-/en/PlusAcc-Vacuum-Magnet-Phone-Holder/dp/B0F18V6PVH/ref=sr_1_15?crid=3TKQZL1VJSVML&dib=eyJ2IjoiMSJ9.rmSgWAN6p7Yr-GodojyjFYmP34cN1V7DF8fpQUqMBOrBWbwVy_KQH1n3_yfTn0KT9SprCL5nedb5_Y00mhlR4orBNJSJYByYH0iuRn9oaydL3f9pMhoxn0UUKscfpBIIPMxWLls_nrso-KlPQRiKVUJVZyufzsGtmIt0HU-VOPbs98hUOxE_DheNCR9XcwXXZMuZ4QqpLw9eiuWTKA-cFcfH82fYykDqNSH95FSU9LMXHKJsvKldX3wyjaX4ZmJdu68h5LT6zZlQo5NGpn1XqTSCfKEl0Qt8-i6pael7D3g.E-reKJhHSjPsFb8t-MWED_UKNaYkCrsD_7dffYcFIqY&dib_tag=se&keywords=compact%2Biphone%2Bmount&qid=1752054918&sprefix=compact%2Biphone%2Bmount%2Caps%2C87&sr=8-15&th=1
If you have another phone brand I reckon you can find something similar with a mechanic clamp on Amazon
