Researching the clown costumes in Halloween '78 & Halloween 4

Hello, I am not a cosplayer or collector, I am just researching the costumes of horror/thriller films for articles I wish to write round about October, especially for ‘evil clown’ costumes in horror/action films.

I have been browsing this forum for a bit; while pretty much all the costumes in each film were bought clothing (especially as all the films were low-budget) I am surprised that I haven’t found anything about the clown costume worn by the actor playing the young Michael Myers in the original film, or the clown costume worn by Jamie in Halloween 4.

Was the clown costume in the original film actually custom-made for the child actor Will Sandin, or was it just an off the rack item or a wardrobe stock item? Despite that there’s commercial replicas for cosplay and trick or treating, I haven’t found any sources. It’s a fairly colourful and well-made design too - maybe it was stock, maybe it was made, or maybe it was a good quality off the shelf item or some kind of family heirloom?

I also am curious about the red and white clown costume worn by young Danielle Harris in Halloween 4; as there’s multiples in some behind the scenes shots, was it a case of multple items bought, or multiple clown costumes being custom-made?

Again I have not been able to find any information on the costuming of the Halloween series. I know that the clown costumes and the mothers white dram sequence dress in Rob Zombie’s Halloweens were custom-made, and presumably the cultist costumes in Halloween 6, but past that it’s a mystery!