Wolfie,
The only way to work out a correct reply is to measure the real thing and to divide by 72.
On a small scale like 1/72, practical matters complicate this general rule.
Maybe your styrene needs to be even thinner than the 0.04 mm you refer to if you want an exact scale, but there's a good reason why you probably won't find much thinner.
Already with 0.04, the styrene glue (or other liquid you use to glue it like trichloreethylene or cellulose thinner, etc...) may well dissolve the styrene. The thinner, the more sensitive to this.
An alternative may be thin paper on which you smear a drop of CA glue. The glue penetrates into the paper and hardens it, almost without adding thickness. But glueing that won't be easy either.
I'd go for the styrene you found there, and use a good magnifying glass.
Good grief you must be blessed with good eyes !