Even if all you do is make it there once a week if they'll allow that could make a big difference.
As far as stretches, groiners are one of my favorites.
Stand with about a shoulder width apart plus or minus some possibly.
Grab your toes with locked out knees.
squat down using your elbows to push out your knees.
Straighten your legs again into the toe hold you started with and repeat.
The good girl, bad girl machine abduction can be used to help wake up the muscles that help track your knees and the adduction can also be used as a stretch under resistance and even help prevent adductor or groin pulls. I don't use the machine to build slabs of muscle or add 50lbs to my squat, but occasionally used for those reasons works out pretty well for injury prevention. Just be sure you don't go any farther than the range of motion you can actively control.
10-20 reps is good for mobility and warmup for either of these.
Edit: Once you can squat wide and you've given it a few to many weeks to try it out and it's not working too well for you, try other methods of squatting. There's also more than just narrow or wide. There's also how much knee tracking and how upright you want to remain.
When you don't push your knees out with the wide stance, you're elminating some of the advantage of the wide stance which is to keep the lifter more upright and keep the moment arm of the knees and hips closer to the bar.