Home Depot has various round wooden tops, but they don't show them on their web site.
Capital City Lumber make round tops they sell through Amazon but they aren't 20". They say they'll make whatever size you want if you need exactly 20"
Capital City Lumber Clicky.Ebay has a variety of them around 20", but not a 20" one that I saw. They do have class tops in 20". Interesting, but maybe not the best for an RV. They do have 19" and 24" wooden ones.
Ebay table topsCall TableLegs.com at 800.748.3480 Almost any diameter to include 20", in three different thickness, and in six species of wood.
Can I Customize My Top?
Easy! Follow the step by step process to build your tabletop. Choose from three different shapes, thickness options of 3?4”, 1” or 1 1?4”, hundreds of size combinations, and six standard species (hard maple, soft maple, cherry, red oak, white oak, and black walnut). Our Table Top Thickness Guide can help you decide what thickness to choose. You can also choose from eight edge treatments. Plus, you have the option of rounding the tabletop corners by applying a corner radius to your top. In total we offer millions—yes, millions—of different combinations of table tops!)
One of these sources will work.
Bill