Most affordable place to get the prescription lenses?

I bought the refurbished glasses at a really good price. They’re the wayfarer gen 2s but i really need my transition prescription put in because my visions getting worse and I want to be able to use these on all of our family outings. Right now i can’t for a long time. Any advice would be so appreciated. I’m willing to buy online and pop the lenses in on my own if i have to