Thats going to be a hard find, most of the old skool Lian-Li PC-60 and 70 cases came with those. Finding them 20 years later isnt going to be easy, I bougt several of those cases and I dont have more than 1 or 2 extra left at this point now either.
That's pretty neat. Or you can just throw and regular standoff and a not with two washers.https://www.bpogsinc.com/index.php?main_page=product_info&products_id=410129
I'd try to use something like this.
6-32 is your standard hard drive thread.
There's an m3 version too like an ssd.