I ordered a stock set for my SA-93, and it finally came in. The butt of the stock is cut for a plate, but my old one doesn't fit. Does anyone know where to get one? Are there different sizes or mostly a one size fits all? All I'm seeing on a Google search is airsoft parts. My old stock is a thumbhole, so it's not a suprise that it doesn't fit on a regular AK butt stock.