Sounds like it was an adaptation of the older song, at the time of the first Irish Army overseas peacekeeping operation in the then Belgian Congo - 60's or so?

I've never heard it, although the Kerry ai-o chorus line sounds vaguely familiar. I think there was a recent (within the last 2 years or so) book published which included soldiers' recollections of the mission. Might be worth checking out. Otherwise, the Organisation of National Ex-Servicemen (if that's still their title) may be the best bet.