I bought a ProClip by Brodit on the UK Amazon site, as it was not available from the US site. Its a 2-piece design, with the mount specific for our cars, and the phone adapter is specific to your phone. I have an iPhone XS Max in a slim Otterbox case and have no issues. Links and pics:
https://www.amazon.co.uk/gp/product/B0040J9EAY (mount)
https://www.amazon.co.uk/gp/product/B00R6OBJJO (phone adapter - at the time they only offered the 6 Plus & 7 Plus, which fit the 10 XS Max fine)
Looks like they now have an XS Max specific adapter here
https://www.amazon.co.uk/Brodit-Pass.../dp/B00NT5XVOA