I also wanted to have a pin mount shower head holder, like the one in the inside shower, but on a suction cup to mount higher on the outside when using the shower. Here’s the pin mount.
Delta Faucet U5001-PK Clear Pin Wall Mount for Handshower, Chrome https://www.amazon.com/dp/B0064TY7MI..._b.QKBbJRQMG0K
I looked into maybe mounting one of these to a suction cup, but it was going to be clunky, so I just got a regular suction cup shower head holder and it works just fine. There are dozens of varieties on Amazon.
Don’t know why Airstream went with the pin mount at all (seems to be a Delta brand thing) rather than the more universal versions.
Easy to install and remove as needed and you wind up with an outside shower that’s like the Living Vehicle one in the video above. I store it right in the shower compartment.
YOHOM 304 Stainless Steel Powerful Vacuum Suction Cup Adjustable Handheld Shower Head & Bidet Sprayer Holder,Removable Wall Mount Support Bracket Stand Clip for Bathroom Accessories,Brushed Finish https://www.amazon.com/dp/B078J2FPNQ..._oiRKBbG5ADZNN