Sounds like a pretty niche use case. Why wouldn't you just use the keyboard on the desk?Is it that hard for any company to make a portable keyboard with quality trackpad built in? I’ve been asking one for years, just so i can use it on my lap while the iPad sits on the desk. It’s would be so ergonomic and such an obvious solution, I’m baffled that nobody makes a good one.
Regardless, I'm sure you could 3D print or purchase something from etsy which holds together a magic keyboard and magic trackpad