Where can I find a LEGO tube piece that is ridged on the outside
Try BrickLink, a site which can solve all of your lego needs. It's pretty useful and relatively easy to navigate. Takes a while to get used to, but it's personally my favorite third-party lego site out there.
Here are a couple screenshots of some of the items in the 'hose' categories. You can buy any item that has been listed by any of the thousands of sellers on the site! It's much better than Amazon, eBay, or LEGO.com/pickabrick in terms of variety, price, and convenience.