Sheet metal is out there but it takes time and patience. The harder part is being prepared to take the financial plunge when the opportunity arises as you don't know when. My brother and I lucked out and found a great set of side curtains and the operator cowling. We were actually contemplating buying the side curtains just to put them in the barn, luckily we were able to purchase the O4 we had our eye on, then immediately bought them. Below is a picture of what we assembled.
IIRC someone did reproduce the rear fenders and operator cowling. You may be able to search and find the old postings, I think on YT.
Like previously stated, W4 fenders can be reworked into OS4 Fenders. You actually have a better chance at finding O4 sheet metal than OS4 as there were half as many OS4's manufactured.
Ohh, if you didn't already know, you have a fairly rare set of outer rear wheel weights that are highly sought after. Last sets I knew of sold for $600.....each.