Check out item #170196018202 on e-bay.  Or, if you prefer a full link:
http://cgi.ebay.com/ebaymotors/GREY-GRAY-PLASTIC-FOLDING-ADJUSTABLE-CUP-HOLDER-10-PACK_W0QQitemZ170196018202QQcmdZViewItem?hash=item170196018202
Is it just my imagination, or do these bear an uncanny resemblance to
some other items offered by our various online vendors? ( e.g.
http://www.busdepot.com/details.jsp?partnumber=CH100G )
Anyway, the seller has ten-packs of these folding cup holders available
in white, grey or black.  Since my van came to me with ZERO working
cup-holders, and since I figure my kids are as good as anyone's kids at
breaking them, I felt like this ten-pack might just be a good value, and
so I ordered a set today.
If anyone knows anything that would make this a bad idea, lemme know.
And if anyone's interested, I'll report back about how it all worked out
when I receive them.