Based off of your comment history, it seeeeems like you live in the US, although I could deffo be wrong. That’s where I live, so I may have good news. It’s illegal to sell tritium products in the US, but it’s not illegal to buy it as an individual. There’s a Taiwanese company that sells all kinds of cool little tritium widgets: https://www.mixglo.com/

that’s where I got my vial from. It wasn’t cheap for what it is, but I think it’s cool.