Microlight fabric that does not cost an arm and a leg ??

I have used silk sold for painting to do a light trouser for sleeping.

weight was 0.59 oz/square yard for 4 usd

Have a Link ??

Perhaps you want habotai silk. 4.5 or 5 momme; 5 mm = 5 momme is about 0.5 oz/sq yard.
"1 momme = 4.340 g/m^2; 8 momme is close to 1 oz per square yard or 34 g/m^2."
http://www.dharmatrading.com/html/eng/4564987-AA.shtml?lnav=fabric_silk.html
http://www.thaisilks.com/index.php?cPath=1_2&osCsid=vvuaan8e5vn6qm9390bi882vb3

Spinnaker fabric http://www.sailrite.com/Ripstop-Nylon-5oz-Dark-Blue-60

Might not be what you are looking for though.

I've found that the nominal weight and actual weight of light silks seem to be pretty close, when I've ordered silk.

But spinnaker fabric will always weigh about twice the advertised weight, in my experience. Some vendors, like Thruhiker, weigh it themselves and report the real weight, but the typical 0.5 oz spinnaker (including the sailrite stuff) usually weighs between 1.0 and 1.9 oz/yd. It has nothing to do with the coating or a conversion from sailmaker's yards. It's just conventional for sail and kite fabrics in the 1-2 oz range to be called 0.5 oz or 0.75 oz. I've asked vendors to weight it for me before I buy, and some have been shocked to find that their own "0.5 oz" spinnaker weighs 1.7oz/yard.

Nm