I had a second set from the hospital, so I don't know where to get another, but I am sure you can find some on the Internet.
I always let my pump run a few extra minutes with just the tubes on after I was done pumping to keep it free of condensation. ?It would blow air through it and you could see the water being pushed out or evaporated.?
I know Rex Hospital's Lactation Station sells them, I'm sure other hospitals might too. Also try a LC. You can call Medela to purchase them too.
You can also run rubbing alcohol through the tubing to help dry it out and sanitize it. That's what it said on my rental pump.
ditto pps--try Rex lactation store and after you pump let the pump keep running without bottles, etc attached to help get rid of the condensation.