I know that I have seen on some bicycle website a trunk bag that is also a small cooler. Anyone familiar with this? I have just bought a flash flag that will require I only use one pannier. One pannier holds my clothing and stuff. I need a trunk bag that will double as a cooler for my lunch. Any ideas?

Get a roll of Reflectix (Mylar foil covered bubble wrap) from a home center. It'll make just about anything a short term cooler.

I used a trunk bag for a lunch box years ago. Though not specifically made for this, something like a cheap bag
from Nashbar will work fine. I used a cheapie and put my lunch in a grocery bag with an ice pack and it stayed
plenty cool.

https://www.nashbar.com/bikes/Product...283_-1___14003

...or you could always use a lunch box as a trunk bag ;-)

Thanks. I'm thinking the trunk bag I have will probably work. I'll try that first.

I have this one (well, the older version) and LOVE it:

https://www.rei.com/product/710404

I have the matching Topeak rack (not necessary, but well worth it), which makes taking it off/on super quick and easy. It has zip down panniers, so you can use one side, both sides, or none. The top also expands. I use the main compartment for my lunch, with a cold pack in there. The rest of my stuff goes in the panniers or upper compartments. Yeah, it's pricey. But in my opinion, it's worth it--the perfect commuter solution IMHO.

There are lots of different sizes, etc. I have the big one and have never regretted having the extra space. I've had it for a few years and it seems super durable so far. Highly recommended.

Good luck.

https://www.amazon.com/Sunlite-Toploa.../dp/B000AO9MC8

+1 on the topeak bag. I got the bag and their super tourist dx rack off ebay for $56 w/shipping. Works great but the grab handle on top is not sewn on very well.

Yes, look into a Jandd trunk bag. I've used one their insulated bags for years to keep all sorts of
things cold or hot.

https://www.jandd.com/search_results....el=2&subcat=43

When you visit the site be sure to check out the specials page for returned and second products that
are first rate but have a very minor flaw (where I got my bag) to save big bucks.

My bag..............
https://www.jandd.com/detail.asp?PRODUCT_ID=FRRP-SPECIAL

They also have those stay-cold bags at many grocery stores that will fit easily in your existing trunk bag. They look like a rather thick plastic bag with a metallic finish. They sell them at all of the major grocery stores around here, and they work fine for keeping things cold and/or frozen in my panniers between the store and home, or home and the refrigerator at work.

I"ve used that one for the last three years. Love it. Good price. Wish it had loops for a shoulder strap though.

Or there's these...

https://www.stonecoldoutdoor.com/catalog.php?cat_ref=3

If money is no object... THIS ONE

Personally, I'd just use a regular soft sided lunch cooler and bungie it down.