Checked eBay and they don't have streamers per se, but you can find people who do custom-made pennants and perhaps could do whatever size streamer you'd like. I checked to see if the woman in Bruce, WI still had pennants advertised and don't see her on there right now--- but she made a very nice pennant in the exact colors and design and size I wanted.
There may be others here who know of a source.
And remember, flaggish things with grommets can be flown on the USS Constitution on your b-day or other important event, to give the item a bit more historical significance. Not sure about streamers, but will check the website of the really big old boat...
Kathy