I've never had the privilege of owning a REAL ITR knob but I use a Duracon knob
And I've driven my friend's EK on several occasions (which has the silver knob). The silver knob does get a bit on the hot side in the summer like any other metal shift knob.

Duracon: Like it advertises. Doesn't get extremely hot in the summertime nor extremely cold out in the winter. It's always at a suitable temperature. It doesn't weigh a lot, only a few grams. So it's not exactly "weighted" at all. I think of it as one of Spoon's many "weight reducing products". My hands aren't huge so the knob fits decently (not exactly perfectly) in my hand. I wouldn't reccomend it to someone that has large hands :P I don't see it as anything more than an aesthetic mod. It's mainly marketed for people who like the feel of a very small and thin shift knob (it's almost like having no knob at all because of it's extreme small size and thinness).