Honestly, as far as latches, I think that "lid" will be heavy enough to seal on its own. I used to think that you need to be completely air tight but that just isn't the case. Besides, a good bit of grease will seal it up nicely. I have had my fire go out after closing the bottom intakes and forgetting to close the top vent. Are you putting a ring around the inside to hold the lid in place? If you do really want latches, there are two types that come to mind. First is the twist type that you find on trunks and cases like this:
You could also just go with a latch like this that would be a little easier to use possibly:
^^^You could probably raid your barn and find a few of these on old tool boxes.