The process meter is a good choice. I do not think you will find exactly what you want otherwise though. »
store.vaisala.com/us/pro ··· M40/hm40 has some very high quality and very pricey humidity and temp sensing equipment - we have some of it at work, and we use their duct and space sensors. If you find an effective and compact solution let me know. To be honest, in my work most of our automation sensors are far more accurate than what we check them with, and it is important to remember that.