Newegg has one, but it's the reference model https://www.newegg.com/Product/Product.aspx?Item=N82E16814202326&Description=vega 64&cm_re=vega_64-_-14-202-326-_-Product
Although AMD hasn't confirmed it, from what vendors said during the cryptocurrency boom, there is a strong suspicion that Vega64 and 56 cards are not being manufactured any longer, especially now since 7nm Vega cards have been confirmed to have up to 32GB HBM2, and HBM2 is still quite rare.