The plane picture in @Chestnut's link uses a bar to retain the wedge, but the one you picture appears to use the wedge-shaped grooves in the sides of the plane for that purpose. My guess is that plane body is an older model. The bar type would be easier to produce, so probably is a newer, cheaper design. The complete plane seems to use a standard Stanley type blade + chip breaker, so the groove in the bottom is probably clearance for the chip breaker retaining screw. You might just purchase an appropriate blade and chip breaker, and make the wedge yourself. It isn't difficult, just tedious.