www.gemplers.com/tubes. They have a complete line of tubes.
Bulk mailing tubes can easily be purchased online at United States Postal Service or at UPS or FEDEX or even in person at the United States Postal Service.
Radio technology has come a long way since the days of tube radios. However, tube radio fans can purchase replacement 6L6 tubes online at thetubestore.
One can get heat exchanger tubes by contacting a company that provides this product such as Phoenix Equipment. One can also purchase online at Grainger.
Here's one place where you can buy them: http://www.tubesrus.com/packaging_materials/paper-tubes/heavy-duty-mailing-tubes/default.html. They take custom orders.
You can purchase test tubes online from scientific supply companies like Fisher Scientific or VWR International. They are also available at many local stores like craft stores, educational supply stores, and some pharmacies.
There are many retailers which sell snow tubes for sliding or sledding down a hill in winter. These items are usually only available in stores during the winter months. Some websites which carry these products are Wal-Mart, Target, Amazon, eBay, Hayneedle, and L.L. Bean.
Maybe you can search Jiangyin Mingding Aluminum Products Co., Ltd., they have various types of aluminum alloy tubes, and they can also accept customer customization. I have worked with them, the service is very good, and the arrival time is also very fast, you can try to contact them.
You can purchase replacement shelf leg tubes from hardware stores, furniture stores, or online retailers such as Amazon or Home Depot. Be sure to measure the dimensions of your existing shelf leg tubes to ensure a proper fit.
One can purchase vintage tubes from eBay where there are hundreds of such items available for purchase. They are also available to buy from 'Vintage Electronics'.
LED tubes can be purchased from most hardware and DIY stores, such as B&Q. Online retailers such as Amazon and DH Gate also carry a large range of LED tubes.
Resistance tubes can be purchased online at many stores. eBay has a variety of brands and levels to purchase as does Amazon. They may also be available at general fitness/exercise equipment stores.