Does anyone know of a rack trunk thats is insulated and could be used for lunches? I'm hesitant to put liquidy leftovers int the pannier with my clothes. Not to mention the panier is not big enough to fit my current lunch bag and my clothes and jacket.

What does everyone else do?

This one is pretty cheap and silver-lined, insulated.
https://www.amazon.com/gp/product/B0016L74Q0

I have put frozen water bottles in this one on 95+ hot Texas days and had to pull them out after 2hrs and keep them in the bottle cage to get them to thaw enough to drink.
https://www.amazon.com/gp/product/B0016L74Q0

Only because I tried what you are asking and it didn't work out well. I found separation for my lunch worked best and the shape that provided that "within" my pannier was this: eBags Slim Lunch Box It's slim enough to have my laptop behind it and clothes rolled up in front of it.

https://www.nashbar.com/bikes/Product...2_167702_-1___ has foam insulation in the sides, you'd still want to use a cold pack in it.

I have one of these I don't use anymore. https://www.amazon.com/Axiom-Columbus.../dp/B001GSQO00 Make me an offer

Those are a little bigger than I was looking for. I was thinking something sized for a tupperware or two an ice pack. I think I'm just going to finde a way to strap a regular lunch bag to the rack.