I am presuming you are taking this with for bait and not own consumption. With no deep freeze you are making it difficult for yourself.
How long do you need to keep the bait usable? 2-3 days? a week?
I would suggest two coolers. One bigger one that takes all the bait(you can get a decent sized Styrofoam one). The chokka should come wrapped in plastic cling wrap. Wrap them in newspaper as well. You then, just before you leave put the bait in this one and you then need to add "dry ice"-do not touch with bare hands! Now tape the lid in place.
You will also need your normal bait box. So when you get to your destination and you want to go and fish, take out just what you need and transfer to your bait box. Tape the lid on the first box again to keep it airtight.
The less you open and close this box the longer it will last.
Only way to keep prawns from going black is to keep them frozen. Once they have defrosted and not used they will start turning black.Once chokka goes pink no good.
The most vile smelling bait keeping exercise that went wrong is chokka! So whatever you do do not let the chokka get ripe!
Good luck