This cheap $30+ unit fits Pint, XR, and GT, under side has velcro sticking to the carpet so the board doesn't slide or roll. Works well for my boards. https://www.amazon.com/Ferocious-Onewheel-Trunk-Stand-Accessory/dp/B07N5LLH29
Others have custom built their own, or use the car holders from FM or 3rd party.
I have this little stand it works quite great definitely not expensive as future Motion one
Onewheel Stand for Trunk (fits GT, Pint X, Pint, XR, Plus) - for All Cars, Trucks & SUVs - High Impact Injection Molded https://www.amazon.com/dp/B07N5LLH29/ref=cm_sw_r_cp_api_i_0218WXKKZNT2KHSWR9TC?_encoding=UTF8&psc=1
Seen some on etsy and found this on Amazon of all places lol but 30$ is a good price point
Onewheel Stand for Trunk (fits GT, Pint X, Pint, XR, Plus) - for All Cars, Trucks & SUVs - High Impact Injection Molded https://www.amazon.com/dp/B07N5LLH29/ref=cm_sw_r_apan_i_CMVW52VV311XKJ6KPBVK?_encoding=UTF8&psc=1
Or this one? Description states for XR and pint and compatible with float plate. I might just buy one. Lol
Ferocious Onewheel Stand for Vehicle Trunk (fits Pint, XR, Plus) - ABS Injection Molded - Fits All Cars & Trucks https://www.amazon.com/dp/B07N5LLH29/ref=cm_sw_r_cp_api_fabc_e2TWFbP1G80W7
A way to transport the Onewheel without having it slam around in your trunk!
>I mean for example, I noticed that the car carrier is different for the GT vs Pint X.
This is not a good reason to choose boards, and is also a great example of why many of us prefer 3rd party accessories.
Car holder, fits all Onewheels, $33: https://www.amazon.com/Ferocious-Onewheel-Trunk-Stand-Accessory/dp/B07N5LLH29/ I have that, fits my Pint and XRs well. It's a little small but does the job.
Other car holder, different sizes for different size Onewheels, $40: https://www.amazon.com/Trunksaver-Onewheel-Stand-Car-Trunk/dp/B07YPWPWTW/
Everything is either 3D printed or custom cut with metal. The base mount is below:
https://www.amazon.com/dp/B07N5LLH29/ref=cm_sw_r_cp_api_i_H6zqFbC6APMP8
As another option, this $32 one from amazon works just as good as OEM. I use it regularly. https://www.amazon.com/dp/B07N5LLH29