My schedule is a mess, fitting in consistent exercise is a nightmare

I work a staggered schedule. I get out of work at 2:30 pm Tues-Thurs. The treadmill at work is always occupied until after 2 pm. Roommate gets off work at 1:30, so on Tuesdays, I can't work out, he is already on his way to pick me up by the time I clock out. So I try to fit in a workout on Wednesdays and Thursdays while I wait for my roommate to pick me up (usually a 30 min wait on those days because he has to pick up his daughter from school).

But on Fridays I get out at 1:30 pm, so I don't get to use the treadmill. On Sats I get out at 12 pm. Again, no treadmill.

So the only days I can really exercise efficiently are Wed and Thu, which isn't enough. I have dumbbells and things at home, and I do use them when I'm home, but between chores, pet care, and exhaustion, I don't do that as often as I'd like.

I'm trying to find a decent used elliptical or something so I can have that at home to use while I watch TV or while roommate plays video games. I hate how FAT I've gotten.