Vertex and other aeration suppliers may have something available.

Many of us just DIY. It doesn't have to be sophisticated, just something weighted to keep itself on the bottom and hold the air-releasing mechanism up out of the mud. IIRC garbage can lids and tires have been used. I made mine out of an old range vent hood:



"Live like you'll die tomorrow, but manage your grass like you'll live forever."
-S. M. Stirling
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