Tracing Missing in action soldiers

I'm compiling the list of comrades mentioned in my Dad's WW2 memoir, which covers several battles incl Dunkirk and D-Day. I have managed to trace most of those he mentioned and have found a record on the Commonwealth Grave website. However, there are a few whom I simply cannot trace, yet I know they existed because I have Dad's photos of them with their names written - even the battle they died in - yet I can find no record. Can anyone please suggest an avenue to follow? I would like to bring closure to these lads and to any of their relatives who may be researching them. They were all in the Green Howards as far as I can tell.
The names are:
1 Private Charlie Lee - Killed in Sicily 1943
2 Sergeant Myson - Killed at Wadi Akarit 1943
3 Captain Shaw - Killed at Wadi Akarit 1943
4 Private R Bristow - Killed in Sicily 1943
Sorry but I have no more info. Nos 1 and 4 photos are at Grim Determination - D-Day if anyone is particularly interested. Many thanks, Paul