Any serious scientific lab supply could help you. I don't have their latest catalog, but LSS (Lab Safety Supply) had a decent selection. Expect equivalent "non-toy" pricing, probably in the $250 - $300 range, certified. There used to be a store in this area, with its University and many pharmaceutical industries, that sold nothing but scientific thermometers - hundreds of kinds of them. I'm sure certain facilities around here have gear that measures in millionths of a degree, but also cost millions of dollars. I'm quite satisfied with my official Kodak Process Thermometer, which I found new, with a bit of patience, for only $50.