Easiest place is through shopgoodwill.com. Tons of beercans go through there. But if you want a good one, troll the for sale section in Dyxum. Their exclusive sales are the best place. Might take a bit. I can give you a heads up when I see one. There might be a couple there now.
Here is one
for $130 including shipping, which isn't a bad deal at all. Here is a Big Beercan
for $165 including shipping. The Big Beercan was my favorite tele-zoom. Has some CA and is big, but snappy and very fun to shoot with. For the best telezoom, look for the 100-300 APO (D or non-D). Finally, here is another Beercan for $110
with shipping included. But, it has microscuffs on the front element. We all know the front element has the least effect on IQ, but I still hate having them.