Noted: According to “The Dictionary of American Regional English,” the massive dialect dictionary produced over half a century at the University of Wisconsin-Madison,one of the first uses of “bubbler” in connection with a drinking fountain was in material from Kohler Co. in Sheboygan County in 1914, citing a Kohler fountain that was “fitted with … nickel-plated brass self-closing bubbling valve … adjustable for a continuous flow of water. … Can also furnish … continuous flow bubbler with above fountain.”
Note that it’s an adjective there, not a noun.
Joan Houston Hall, former chief editor of the dictionary, told Wisconsin Public Radio in 2015 that “bubbler” usage “mirrors the marketing area of the Kohler Company of 1918 or so,” chiefly in eastern Wisconsin, and especially in the southeastern corner of the state.