CDK if you decide to go the non-cooler close off. I have one I can spare, in my parts collection. I may even entertain a straight swap if you decide that is best. FWIW
Depending on how complete your sled is at the moment, you should be able to remove the appropriate fastners appy some heat, where you need to break the glue bond, and sneak the cooler out and sneak the new non-cooler close off back in without a complete disassembly. Wedge it in the appropriate spots and re-appy the adheasive, and torque everything back up.
I'm strongly considering building my own front closeoff cooler as well as an under tank double pass cooler out of a 6000 series structural aluminum alloy extrusion, to get the water weight closer to the COG of the sled and eliminate the stock weak / non-structural 5000 series aluminum coolers sticking out the back and attracting / making wet heavy snow / ice. While the "T" slots are convienent, IMO they are not worth the weight penalty being a non-structural alloy. Had they extruded them out of 6061-T6, I'd stay with the stock design, or at least leave the top Half of the extrustion from the seat back for the utility. As it is they are going, bye bye. FWIW