You can probably design something really cheap that will collapse out of a "cylinder" of stainless(pot,decanter,ikea silverware basket,etc.....if you cut the cylinder walls into 3 vertical pieces that join/fold/lay together somehow creating a lot less space than the full cylinder when packed..with a flat top grill
maybe even holding the side pieces together..maybe some offset flanges top and bottom to slip onto those pieces..like every other half inch of the side ends bent the opposite direction in and out for slipping over a straight edged bottom.
Keep in mind that mechanical ductwork installers generally can add a circular "attached collar" to the flat side of a duct by just cutting the end of a piece of round duct every half inch..then bending out every other one 90 degrees.They then cut the round hole,the ones that are still sticking straight out are stuck through the hole and bent over against the back of the flat piece on the inside..holding against the others that were bent already against the outside of the metal.
It's a very simple strong method of attaching round ducts to main ones without having a special expensive part
with a collar attached and having to screw it on around the collar.it actually turns out pretty airtight also with only very tiny holes between tabs.
My stainless camp stove...Someday I will adapt a 2"x3" long downspout piece on that way as a chimney outlet,a little jbweld for the tiny holes,3-4 screws through the outside bent flanges and it's good to go and cheap..using a short galvanized downspout piece for the chimney bottom and lightweight aluminum for the top portions..I have crimpers and can cut the top pieces to about 18", crimping one end so it'll fit inside the other..works for me!
If I find that stove takes more than a 2" chimney to burn right,I'll scrap it!