eBay; look for one being sold by a lab and not one of those hand held things. I picked up a Phillips O-scope for $35 a while ago and it had a calibration sticker on it from Fluke that wasn't 90 days old. Absolutely stole it.
I'd also check out Craigslist and see if a school/community college is having a fire sale. Not sure when their budgets expire but it's not uncommon for a school/university to sell perfectly good lab equipment in order to use every $$$ of their allocated budget.