Where can I find wort to buy online?
The only wort for sale I know of is either malt extract, liquid or dry or something like Fast Pitch https://www.northernbrewer.com/products/fast-pitch-canned-wort-4-pack used to make a yeast starter.
What is it you are trying to do?
You do extract. Or all grain. Brewing. For allgrain. Not sure of you you can buy. Wort online. Could be but never did see it
Extract is basically unhopped wort. But there are hopped extract companies out there like Mr. Beer and Muntons.https://www.muntons.com/beer-kits/
I got my start with Mr. Beer and made some great beer.
Wort concentrate just add water