Ramp for backseat

[PollyPutTheKettleOnKettleOn]

Think this might be a long shot but I'm looking for a ramp for a large elderly dog who uses the backseat, so the ramp needs to fix adjacent to the backseat / in the passenger doorway.

Any ideas?

Can only find them for the boot!

Open to second hand (in case anyone's selling )

I use a boot one for my back seat in one car and it’s fine- it doesn’t work in the other because the door bucket gets caught on it.

Can you fold down half of your back seat so the dog walks to his/her seat by walking through the rear door?