Like this? http://www.walmart.com/ip/Hagen-Marina-Plastic-Aquarium-Thermometer-Plastic-Thermometer/48184773
Or are you talking about a probe thermo?
no glass floating type is what you want . the will fit it in some humidity vent holes but are to short to use like that . they will work laying down though . you can adjust your little thermometer by sliding the tube in the little metal straps a little bit.
Aquarium floating thermometer the cheap one will do fine use the search to see it .one line it is very cheap. in the store $3