Working as a bespoke tailor it isn’t possible for me to make such clothes cheaply. After all a child’s jacket still has two sleeves, a collar and lapels as well as the necessary pockets and detailing.
As an answer I have always pointed them to eBay in search of bargains.
Just to show what can be found, here are half a dozen items currently available, or recently closed.
This shows the price range of options available, so keep searching – they are out there.