Any bike shop with a QBP account can get Winwood Decksters, they are plate aluminum
you screw in a spare SPD cleat.

in fact anyone with a hacksaw a piece of plate aluminum or
plywood, I suppose .. can make one,
wood, 2 T nuts, threads chased for 5mm ,
to screw in the flat head cleat bolts will do .
stick a safety piece of tread tape from hardware store , on top.