Yeah I’m not aware of much out there. Cocorahs does have ice accretion reports, but it’s difficult to navigate the obs and there aren’t that many. It may be in its infancy stage…not sure.
https://www.cocorahs.org/Content.aspx?page=ice-accretion-pilot
Of course the ASOS accretion obs aren’t a direct caliper measurement, but rather a remote sensing estimate.