Re: car seat holster
I agree I've never seen an under-seat handgun holster advertised. It does sound like an easy do-it-yourself project though. The main thing is to have the holster secured well enough that it won't move around once installed. You might reach down and come up empty-handed.
If it were me, I'd look around at the next gun show for a holster with lots of attachments for straps, like an old shoulder rig or a thigh holster with thumb break. Both types are designed with plenty of loops for securing the holster with leather or ballistic straps.
The other thing you could consider is to acquire a left-handed holster and attach it to a wood base which would be secured on the floor below the seat. The angle of draw should be the same for either method if it's done right, and the holster should not move at all. You'd still want a right handed thumb break with a leftie mounted to the floor.
The thumb break would be a must for me, because I've stopped fast often enough to know what happens to anything loose under my seat -- it winds up sliding around under the pedals.
The Second Amendment does not exist
to protect the gun rights you like.
It exists to protect the gun rights you hate.