Something like this would work - a few people have used similar things - the small part screws to the front of the lid and the longer part to the front wood of the enclosure and then you just clasp it together or just unclasp it. While it's quite a height to reach, some lids are not that heavy for a hamster to push open and they always find a way up there! All they have to do is pile the bedding into a mountain in one corner and walk up! I've seen that done before. Clever little things.
Or some people just put a couple of books on the lid at each end
Check for chewing as well just in case he is a chewer and chews the wood.
Catch latch