Ben needs a waterproof kite!

Hint 1 of 6:

Only one item in any time is designed to be waterproof.  Make sure to pay
close attention to the item descriptions.

Hint 2 of 6:

Something in this time can be used to keep away rain.

Hint 3 of 6:

Red Edison's lab coat looks like a raincoat, but only employees can take that
coat.

Hint 4 of 6:

You need to give Red Edison proof that you are working for him.

Hint 5 of 6:

Or at least proof that he needs someone working in his lab.

Hint 6 of 6:

Give him the "Help Wanted" sign from the motel's window in Bernard's time.