drain cap

When I bought the house in 2018, gutters connecting enclosure to pool came with no guards and no end caps. See pics below. Leaves accumulate like crazy without guards. Not sure if end caps where left out on purpose to allow side drainage. Not sure if guards were left out on purpose. Is this...

I Misplaced the valve cap for the 18x48 coleman pool. I Can’t find a replacement online in stock. Can anyone help me with what I should use? I have bought 3 pvc pipe caps, one 3/8 in, one 1 1/4 in and one 1-1/2 in. Im at a loss and have company coming soon. Please help :(