[Shane826]

Of the options you’ve listed the only one I would consider getting elsewhere is the A/C. And with that your options are limited if you plan to store it on a garage with a 7ft tall door. Other options are either very TM specific or would require a bit of work to install.

Also note the vast majority of stock order TMs are already gonna have A/C, awning, front window, propane hookup, radio, and TV antenna. The cassette toilet might be harder to find.