For you Z3 and Miata drivers, have you considered a
Safepacker by The Wilderness?
I have one, and it works as advertised. You carry the gun "concealed out in the open" and you can attach it to your seatbelt. If you have to leave the vehicle, you take the Safepacker with you, and your gun is still concealed.
I don't use it every day, and I don't drive a convertible, but I do use it with some degree of regularity, particularly when I need to leave the house in "house clothes" as stated above in a previous post, and want to carry without bothering with a holster and a belt.
Another possibility, of which I also have one, is the
Versipack by Maxpedition. Both products are great for those times when you need to grab a gun and go without the need to "dress up."
“Hard times create strong men. Strong men create good times. Good times create weak men. And, weak men create hard times.”
― G. Michael Hopf, "Those Who Remain"
#TINVOWOOT