Milo

Hi, I need to use spiral blades but the used Ryobi I just bought doesn't seem to have thumb screws to clamp non-pinned blades. It looks like there are two holes for them (one on top, one on bottom). CAN I buy thumbscrews to clamp non-pinned blades? If so, WHAT SIZE THUMBSCREWS should I buy? Thanks a lot, I greatly appreciate if anyone knows about this. I know it's a basic question but I couldn't find the answer on any forums...