Is passing around resources in research a common practice? I

yeah, super common. if it's legitimately rare they probably won't give it up (at least not without money/trade), but for something like a cell line, i'd be surprised if a lab had some but wouldn't share it. and even for reagents, if you only need a tiny bit for one experiment they might still share for free. i see people borrow a few microliters of restriction enzyme now and then

also see if you have a cell culture facility on campus, they might have stocks of those cells.

also the better bet if you're worried about people not giving you something: ask a grad student, not the prof. unless the lab is brand new, the prof hasn't worked in the lab for years to decades, they don't know what they do and don't have. but if you throw a six pack or two at a grad student you can get anything you want