Road2HardCoreIron

Unfortunately, the best machine for the lower quads is the hack squat, so the only tip I can give you is high quality knee sleeves. I like Cerebus Strength's Triple Ply Knee Sleeves. Anything neoprene is garbage. It might keep your knee warm, but it does nothing for stability and protection. Brian Shaw's Extreme Sleeves are also great. I have them for my elbows. I actually rarely use them, but the powerlifters and strongman competitors burrow them all the time when benching. They say the compression is so great it gives you 30-50 lbs on your bench.

You could also try, but I am sure you already are, single leg extensions and Bulgarian split squats set up to be quad dominant.

The final thing I will offer, close your eyes, block out the noise and focus on the muscle you want to grow throughout the movement. Crazy how you can transfer load by blocking out all the other distractions. I use this technique when I am just not feeling an exercise.