UV dye and a little UV light will run you about $30 for a supply that will last you years. They are readily available on auction sites, the 'Zon or automotive stores. Just make sure you get a dye that is compatible with hydraulic fluid. The expensive part used to be the UV light, but now there are UV LEDs which reduce the cost of the light to as little as a few dollars if you want to go on the cheap side. I just bought this http://smile.amazon.com/s/ref=sr_qz_back?sf=qz&rh=i%3Asporting%2Ck%3AKMASHI+12+LED+UV+Light+Pets+Urine+and+Stains+Detector+Ultraviolet+Flashlight+Blacklight+Pet+Dog+and+Cat+Urine+Stain+Finder+Detects+Human+Fluids\c+Counterfeit+Money\c+Bed+Bugs+Scorpions&keywords=KMASHI+12+LED+UV+Light+Pets+Urine+and+Stains+Detector+Ultraviolet+Flashlight+Blacklight+Pet+Dog+and+Cat+Urine+Stain+Finder+Detects+Human+Fluids%2C+Counterfeit+Money%2C+Bed+Bugs+Scorpions&ie=UTF8&qid=1459883645 and http://smile.amazon.com/Spectronics-Tracer-TP34000008-Dye-Lite-Spectrum/dp/B000NPGXJO/ref=sr_1_2?s=automotive&ie=UTF8&qid=1459883736&sr=1-2&keywords=dye+lite just to have on hand.