Your local auto part store should have them.
47065HP is the part number and yes add a small amount of RTV on the ends to help seal better.
Zero need for RTV. All I ever put on them is a little bit of coolant to lube them. My plastic ones never leaked for over two years and only got changed to aluminum because the plastic one blew.
2011 Mitsubishi Lancer GTS - DD mode
1991 Mitsubishi 3000GT - Many mods to come