A pool supply store should sell very cheap plugs for both the inlet and skimmer - seems like less than $5 each.

The inlet piece is just a screw type cap.

The skimmer plug is just a rubber plug with metal washers at both ends and a screw with wingnut through it. You push it into the skimmer outlet and tighten the wingnut, which compresses the ends and expands the sides to where the skimmer is blocked.