These are rather expensive.
I have an R-12 detector made by Snap-On that I purchased 5 years ago for $60. Imagine my surprise to learn that the thing cost about fout times that new.
I think you need a separate tool for R-134. These come with a sniffer sample a small vial that can be used to test the device. When it senses R-12 or R-34 it beeps faster and faster.
I would try E-bay. Look for Freon Leak detector or just leak detector.
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