Thanks for all the suggestions guys. I was looking at the gaskets from Williams/Kegworks. Although the gasket that came with it was new and provided a very tight seal, I had to really put some force into closing it, I will give that a go first, and then try to move the metal as a last resort.
If all else fails, I had already thought about making it a vessel to store sanitizer and other stuff.
Thanks again for the quick responses!