Go to pcpartpicker.com and select Individual Parts, and then click on Memory.
You will then see a massive list of memory appear. And a search box. Type "DDR4 3000" into that search box, and the list below will filter out all other memory and you will have a list of what you are asking for.
You did not tell us what motherboard you have. But what you should do is go to the web page for that motherboard, and click on the Support link, and find the QVL (memory compatibility list), and from that list, you can pull memory kit part numbers, and drop the part numbers into that search box on pcpartpacker.com, and it will show you a price. That will be the best price that any of about 20 companies was offering that exact memory kit for. Its an...