A stirrup is basically just what it sounds like, a stirrup. I can make one out of a leather strap and stirrup. It attaches to the outer front seat bolt and easily swings out for ingress and in for egress. Something like this.Rope ladder?
https://www.jeepcargonet.com/2016-02-10-05-56-18/prod92-7/56-jeep-stirrup-step
It works well for 5’4” women and little kids.