I’ve always just bought cheap ones on amazon.I think it was this one. They have lasted 3 years on my camelback no problem. I even braided three together, they’re flexible and I just sewed them in with thread but recommend fishing wire. It’s a lot tougher and clear.
just make sure you buy the ones that come directly from amazon! They are about a couple bucks more expensive but they ship faster so it's worth it!
edit: Link