When we go camping we need to pack the back seat of my 2005 Mini Cooper S Convertible to the absolute brim with gear. Unfortunately, that leads to us needing to keep the convertible top closed to avoid flying objects (Your Palmoliiive!!).

I'd like to sew a custom fit tarp (maybe with a zipper!) that would cover all the gear and hold it securely that is form-fitted enough to still allow the convertible top to open and close.

What's the best way to get an interior 3D model of the cargo area, hopefully in Sketchup that I can turn into a seeable pattern? Is the a way to 3d scan myself? Maybe an app on my phone? Or are such models in the public domain? Or provided by car makers?

I know Sketchup and am familiar with furniture design, but I've never needed a model of a complex form that already existed IRL. I'd appreciate any advice. I did some googling and I can find generic models of Mini Coopers, but not of the back seat area and not identified by specific model.

Thank you.