Few folding shovels pass the "Doug Test." I open them up, hold in a 45-degree digging position with the tip on the floor, and surreptitiously put my body weight on it. If there's flex in the blade, forget it.
I found one years ago at Lee Valley tools. It wasn't in the catalogue. It weighs a ton but at least it works. The 90-degree "grape hoe" function is sometimes handy.
Contractor grade floral shovels with shorty handles are actually much better value, and weigh less.
The best deal is a $2
yard sale shovel with a cracked handle. Chop it short and sand it down. Voila, now you've got a real shovel that fits in your car.