How much gold and how much time does fitted mithril or adamantine armor cost in D&D 5e?

I’m looking for the most widely accepted rules for buying mithril and adamantine armor, including chain, splint, half and full plate. How much gold and how much time for a merchant to craft does each piece of armor listed (8 total) cost, baseline? Non official rules are allowed as long as they are widely used. I’ve scoured many sources like the DMG, in addition to the other official 5e sources.