coolant bottle cap leak skidoo 2007 800 GTX

I have seen a number of entries regarding the rad cap on the coolant bottle with regard to the cap not fitting, leaking etc. Got the same problem on this sled I recently purchased. Coolant leaks from the cap and cap very difficult to put in place. Purchased a new cap ( 509000187 Pressure Cap.) and same problem occurs. Comments I have read include the coolant bottle warping with engine heat. Purchased a metal ring insert to true the tank opening but that hasnt done the trick.
anyone have an idea of a different cap other than the oem or kimpex cap. I was even thinking of adapting a different filler neck.

coolant bottle cap leak skidoo 2007 800 GTX