I've done some searching, and I've not really found a solid solution for the broken climate control knobs, at least on the 95-96 cars. Occasionally, an OEM one pops up, but it's used and likely close to the end of its life, much like the ones in my car. My old temperature control knob is just for looks, as it's broken inside and barely grips the shaft of the climate control unit. This may work for you, or you may hate it, but it's a solution that I think works well enough.
I found a set of climate control knobs from a 94-04 Mustang and thought they might be close to what we've got in our cars. Here's the Doorman part number on the box.

While it's a close fit, it does need some modification. The shaft in the Jaguar climate control is just a bit larger than what this is designed for. So I broke out my trusty plastic welder to extract the metal sleeve in the new knob.

While the plastic was still hot, I jammed it on the shaft of the climate control knob and after cooling, it works really well and looks great. I'll do the other one to match Shortly.

I think the older Fox Body ones might even be a better fit if someone wants to try those out.

 

I was able to glue the pieces of my old one together, and than I tightly wrapped wire around it for extra strength.

 

I did something similar, but used strong sewing thread wrapped around and saturated with superglue. Extremely strong.
Jon

 

I also repaired and reinforced the one on my XJS '96 with a small steel bush

 

I wish I had the broken pieces of mine to fix it.