... CR-2032 batteries ... There are Chinese sellers who have them in bulk packs on ebay for only pennies per battery. A 100 pack would probably be a good investment for almost anyone who has a lot of old hardware lying around that needs at least one of these.
Beware that much of that cheap stuff from ebay is just junk lacking even half the ~225 mAh capacity of a real CR2032 (= wil last far less).
They also love faking capacitors:
and whatever can be faked.
... What do you guys do with old batteries? I've been vaguely aware that they shouldn't be thrown into the bin, but that's exactly where I've put them all my life. I've done a bit of research and discovered that there are numerous places near where I live which accept dead batteries to be recycled, who knew?
Whatever you do, EXTREME CAUTION when there are little children around. A button battery looks like candy to them, so they swallow it, then they die.
A tip regarding computer CMOS/RTC lithium batteries: If the system is going to spend time unplugged from the wall (and/or PSU switched off), say several months or longer, better write down/save the BIOS settings and pull out the CR2032. This will prolong battery life and prevent battery spills on the mobo.