I have a few converted fire extinguishers. the valves are about $30, hydro test is about $35, and then a fill. Great way to get a tank relatively cheap compared to a new tank + fill.
btw, I know a guy here in Moncton who set himself up with a 60LB filling tank (dip tube to the bottom of tank) and fill his buddies' 5 pounders for them. he charges just enough to keep himself in free co2...good deal all around.
Would be ideal for someone in Fredericton to do, BUT does take some time and effort on someone's part.