In terms of weight training you've pretty much covered them all. But I'd definitely toss in cardio that works those muscle fibres too, which is pretty much anything from walking, jogging, cycling, swimming, rock climbing, etc. to practically any team sport that involves some movement beyond golf.
If you are adamant on doing different leg exercises then just youtube search for yoga/pilates stretches involving the leg muscles and pick and choose ones that you like. Otherwise use one of those bodybuilding websites with 15-30 seconds videos of people using dumbbells / freeweights / etc. to stretch a specific muscle and pick different ones that you haven't done before. Basically though between the four exercises you mentioned you're covering all the major muscle groups. The yoga/pilates (which is really just stretching with some meditation stuff thrown in) will also help to focus on strengthening the ligaments and tendons as well as helping to prevent any injuries to the muscle fibres in your legs.