Wall shelf for VPI Super Scoutmaster?

Rob, You get these https://closetmaid.com/webapp/wcs/stores/servlet/en/closetmaid-us/maxloadbracket and the matching standards and wire shelves then you can bolt anything you like from MDF to granite to the wire rack. You can make a valance under the shelf to hide the wire. I would use solid surface material like Corian. MDF is easier to work with and you can Formica it. This way you can make a shelf exactly the size of the turntable which will look sharp. 

Target makes a wall mount platform brace that is gloss black 21" x 19". Theoretically you could mount a second platform board of your choice on top of the current set up at the detentions you desire. 

@ghopat,

I used Mana wall mounts for years. They came with glass shelves but you can use any material. I ended up using  BDR. If interested, I still have several.

Another idea to go with is similar to @mijostyn has proposed. 
This is a different bracket system along the same lines.

https://www.amazon.com/CUZURLUV-Shelf-Bracket-Max-Load/dp/B07VN219GV/ref=sr_1_7?dchild=1&gclid=C...

I'll note that you MUST hit the studs (16"oc) with each bracket. I would use nothing less than (3) #12 screws 2 1/2" long.  1/4" lag bolts are even better. Two may be enough if you use 3" rather than 2 1/2. You can use your own shelving and allow it to hang over equidistant on each side. You might try a maple cutting board for the shelf. If you need further assistance just email me