I ordered this from Home Depot: Aspectek 200 ft. Double Sided Holographic Bird Scare Ribbon Tape. Took about a week to ship to my local store. They have a similar tape that is thinner which would probably work, too.
Key is to tie it so that 2 to 3 feet is exposed to the wind & freely flaps in a breeze. Makes some noise & flashes. Doesn't seem to bother geese much, but cormorants are a different matter.
