My apologies few are interested in accurate and fewer still are willing to pay for it.

This is the one I use at work it is very accurate and very good. I have no complaints but the price tag. It isn't something you might leave in the enclosure at all. I have not seen an accurate dual one most are moderate accuracy at best.

http://www.bkprecision.com/products/...ygrometer.html

+/-1ºF and 2.5% accuracy it isn't horriable but not great either.Semi-Reasonable price you get what you pay for.

https://ecat.fishersci.ca/(S(hj1tev4...spx?cid=200619

or

http://us.flukecal.com/products/temp...duct_details=2