Marginal plants for VERY small pond (Knighton LD7)

I have made a pond out of a plastic storage crate after finding a dehydrated frog in my garden. A friend is kindly giving me some floating pond plant, but I would like to add one or two plants around the edge. But all the mail order companies I've looked at only sell huge pots that would almost fill my pond! If anyone has a tiny piece of plant they could spare, I'm sure the frog would appreciate it. Thank you.