Temperature/Humidity Sensor/Controller

What is your location? How easy is it, to source from other countries?

Yep. Telephone the oven manufacturer for advice, and go from there.

http://search.yahoo.com/search;_ylt=Am0ZgPdDQNoY2RdTAHK.aiebvZx4?p=humidity%2Ftemperature+sensor+&toggle=1&cop=mss&ei=UTF-8&fr=yfp-t-521

Get it from your laboratory oven chamber's manufacturer.

If these guys don't make it, it probably doesn't exist.

http://www.watlow.com/

We use their stuff in all kinds of applications.

Good luck with your quest.

In the trade, temperature and humidity sensors and controllers are known as 'instruments'.

Sensors and their dedicated digital displays are relatively easy to install, but control of either variable involves a significant learning curve. Modern instrumentation is one-size-fits-all, so you have to know the industry jargon and the specific details to program it to get it to work.

If you have to ask where to buy the sensors or the controls, you're not likely to have the experience to easily get an environmental chamber or oven up and running.

The vendors (distributors) of 'process' temperature and humidity controls (as distinguished from 'HVAC' office/home/warehouse controls) typically have a service group that can install the instrumentation or can recommend a firm that can.

I suggest you look for a distributor who can provide service as well as sell the instruments.