Lunges? Box step-ups or step-downs? Pistols? There are lots of free weight exercises that work the quads and glutes. One of the more creative is the hip belt squat:
No lower back (or any upper body) load there.
But I guess if you want the load-it-heavy-the-machine-will-save-me effect of a leg press device, you'll have to build one. Make sure it has stops that prevent you from getting squished. For the loads a strong person can leg press, you'll probably need to bust out the welder and find some steel tubing. Post up when you've got it!