If you are looking for an unexpensive protection, Aluminum Round skids are what you are looking for.
9mm is right in between ¼ and ½ inch. Not too big. Not too small
It comes with 1 M6 Hex bolts (20mm or 25mm) and a 1 countersunk washer. The bolt has some blue glue on the tip to reduce the chance of come unscrewed 
 
Diameter: 35mm (̴1.38 “)
Thickness :9mm 
Note: M6 bolts lengths are 20mm and 25mm including the countersunk head (available threads are:  16mm and  20mm)
 
Alessandro’s tip:
"I found them a great solution to protect parts of the splitter that touch not so often the ground. I suggest 20mm bolts for alumalite 10mm sheet, and 25mm for the ½” plywood"