You can buy a ready-made kimono in antique / recycle kimono shops, antique flea markets, online mail order and auction.
Brand-new ready-made kimono called "Preta".
"Preta" is a shortened from of the French word "Pret-a-porter".
"Pret-a-porter" means high-grade and ready-made.
But in kimono's world, if only it's ready-made, it's called "Preta", whether it's high-grade or not.
In "Preta" kimono, there are not only silk but also chemical fiber.
The chemical fiber used for kimono is mainly polyester.
In recent years, polyester is difficult to distinguish from silk.
Also, in summer, a lot of "Preta" yukata (cotton kimono for summer) appears too.
Some famous Western clothes makers are selling ready-made polyester kimono and ready-made yukata.
"Preta" kimono is generally low-price than custom-made.
It is not your own size, it's usually M and L.
But to wear it is not so difficult.
However, "Preta" kimono is not only one item.
Very occasionally, you may find the person who wear same kimono as you.
And polyester kimono is considered to casual, even if it is very expensive and high-quality.
You can buy "Preta" kimono in some Gofuku-shops, department stores and online mail order.
Also, some antique kimono shops are having "Preta" kimono too.
One more type of ready-made kimono is used kimono.
Basically, used kimono is still more reasonable than "Preta" kimono.
And sometimes you can find a good vintage one.
The kimono made after later-Showa period have good condition especially.
In that period, technique around kimono was growing up.
But people were becoming not wearing kimono.
Now, a lot of high-quality kimono of that period are sleeping in their closets, are passed into used kimono shops, and are sold.
You can buy used kimono in antique / recycle kimono shops, flea markets, online mail order and auction.
Also, often antique kimono events are held in department stores.