FCP Euro has them: https://www.fcpeuro.com/products?keywords=61667467951

You may have to do what I did when I replaced mine, drill a small hole in it. The replacement cap was a tighter fit than the original and wouldn't allow the air in the tank to escape when it was heated up. That pushed the washer fluid out through the washer nozzles. I think the original fit looser and allowed air to escape. After I drilled the hole, no more problem.