There are many USA vendors selling rebuildable tanks for reasonable prices, and certainly many vendors on ECF are trustworthy and you have the ability to communicate with vendors here if anything goes wrong with your order.
You could also look at vapecrawler.com, if you input the atomizer or whatever vape equipment in there, you will see a variety of decent prices (not always the lowest, but decent, as vendors do pay a percentage to vapecrawler to be on there. Also, sometimes the least expensive vendor may not be the most reliable vendor either, but it might be a place to start to get a sense of prices, overall.
China vendors, many can be quite reliable and inexpensive as well as offering free shipping. I am partial to Fasttech and 3FVape but everyone kind of has their favorites. It can be a good place to pick up things at low prices, but the downside on that is you will have a 2--4 week wait, so if you want something faster, you'd probably be better with a US vendor, although some of the Chinese vendors can be great for things like extra wire, wick, tank .parts and etc.
Best of luck in your search!
Anna