Where is a good place to start looking for used equipment here in Fort Worth, I've already tried Ace?
Search these catagories in the Yellow Pages:
Ice Making Equipment & Machines
Ice Making Equipment & Machines Reparing & Service
Restaurant Equipment Repair & Service
Restaurant Equipment & Supplies
Also, check the classified ads in the Star-Telegram.
Sometimes the repair guys buy non-working units for scrap (or get them for free for hauling them away) and refurbish and sell them for cheaper than working units available from some of the buyer/resellers. I had a BIL that used to do this. That's why I included them in the list of places to check.
There are a lot of places going out of business ... many will try to sell their equiment via the classified ads before they resort to selling to a used equipment buyer. They can get a little more than the used equipment buyers are willing to pay - but less than what they are selling the same thing for.
The key is to shop around and know the market.
I doubt you will have much luck finding something as small as a 50-lb/day unit - but a couple of years ago I found a couple of 250-lb/day units ranging from $500-$800.
Of course - you could always buy a freezer and make your own ice. A gallon of water weighs 8.34 lbs - so 50-lbs of ice would only be a matter of freezing 6 gallons of water (which you could divide up into whatever portion size would be most convenient for you to break up for you applications).
Happy hunting!