They are called "Caravan RV picnic folding External Table" and come in several sizes. Depending on the mfg, they are powder coated aluminium, or some type of ABS plastic. They are on Ebay US and Ebay AU, then I also found them on AliExpress.  Yes, I will have to drill holes for rivit's or screws to attach the table to the siding, but i am ok with that as long as the product is built out of quality material. Here are some links so y'all can see what I am talking about:

https://www.ebay.com/itm/Caravan-RV-Picnic-Folding-External-Table-Quality-Black-Aluminum-800-x-450mm/302345224234?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D55992%26meid%3Df5e8e89bad78450cb96582ee1d38e88b%26pid%3D100005%26rk%3D3%26rkt%3D5%26mehot%3Dlo%26sd%3D302258688759%26itm%3D302345224234&_trksid=p2047675.c100005.m1851

https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20190204065423&SearchText=caravan+rv+picnic+table+

https://www.ebay.com.au/itm/Black-Caravan-Picnic-Folding-External-Table-800-x-450mm-RV-Camping-Outdoor/322920583322?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D20140106155344%26meid%3Dca694a2af28c4bd0bac127f0172ba163%26pid%3D100005%26rk%3D3%26rkt%3D5%26mehot%3Dpp%26sd%3D181782642305%26itm%3D322920583322&_trksid=p2047675.c100005.m1851#shpCntId

Anyway, I like the idea. I wonder if we could do a group buy and get the cost down under $200 delivered for the 450mmx800mm size?

I could build one slightly cheaper, but not sure if it would be as nice and it would take some effort. 

http://smile.amazon.com/gp/product/B00KH03U5A/ref=oh_aui_search_asin_title?ie=UTF8&psc=1 - Folding Table.

Another easy way to go might be a removable table, using some of this "track"..

http://smile.amazon.com/gp/product/B004OHTRE0/ref=oh_aui_search_asin_title?ie=UTF8&psc=1 - Table Mount.

Brackets:

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dlawngarden&field-keywords=16%22+stainless+folding+brackets

I do agree that proper placement would be critical, since moving it would be verbotten. 

Given that the outside measurements indicate (if my calculations are correct) that the table linked above is less than three feet long (outside frame measurements, table would be less), I don't think the cost is justified, even if it could be gotten down to less than $200. 800mm=31-1/2"; 450mm=17-23/32" or 2.62'x1.48'.

Edit: You could possibly use something like this which is available for a whole lot less:

https://smile.amazon.com/Haitzu-Tailgate-Support-Wrangler-Aluminum/dp/B07F3YHFRB/ - https://smile.amazon.com/Haitzu-Tailgate-Support-Wrangler-Aluminum/dp/B07F3YHFRB/

I am looking at small griddles, like the Blackstone 17" propane(my current grill/griddle from the motorhome is way too big). If cooking on that I would have to be careful not to melt the table base when cooking.

pics of the process in the slopod link below.

(I now have the pod back)

Offgrid,

Mine is made out of a thermally modified pine, Pakari is the brand and its used for decking and siding.

I use the 3/4 skirt boards. Super light and very stable.  http://www.pakaritmd.com/ - http://www.pakaritmd.com/

Anyway, I found a company in China that makes the 430x950mm aluminium tables. Still negotiating, but might be able to buy 20 of them for under $100. Not a big fan of powercoating since it has to be done right or it won't last a year in the 'weather'. 

I still like the HDPE idea because I like the look. And the stuff is easier to work with than wood. It does not warp, splinter crack or chip, the color is molded in and it's weatherproof.  1/2" thick x 24x36 black textured board runs $62 shipped. Add a piano hinge, screws and hardware would put the total at about $100. Going HDPE and stainless hardware would be bullet proof, so right now I am leaning that way. 

Furpod, sorry about the long links and will try your suggestion next time I need to post one. And are you talking about the HyperLink box? I don't seem to have a spellcheck box either......nevermind I see it on the Quick reply. 

Motor7, how well does the HDPE resist ultra-violet light?  That seems to be a problem with many of the plastics options available.  Also, HDPE is kind of "bendy" if it is thin, so how thick do you propose to make the shelf to keep it rigid?  

Once you get past the UV resistance issue the possibilities really depend on one's creativity and aesthetic choices from utilitarian practical to zany.  For myself, I would like to consider matching shelves on each side made from molded fiberglass that look like stubby airplane wings but that's a very long way off.  ;--)