pm mordalphus or nilocg on the forum here, there's no more powerseller section. if they can't help you out, search e-bay, pretty much all of them on there will work, but stay away from the nano ones as they are hard to fill w.o syringes and IV tubing (which is how I have to fill mine, long story) alternatively, you could make one quite easily. search DIY dropchecker and you'll find something. bromo blue is found in pH test kits or in a high school chem lab, whichever's easier. 4dhk soln can be made from baking soda, search DIY 4dhk and you'll find something.