I know there are already lots of boxes that kind of represent guardsmen from WH and anything similar BUT, nothing is close enough to Halo CE marines. It's pure nostalgia but I've been searching long and hard and haven't been able to find something. Not sure if they would sell well but I know I would buy them in a heartbeat.
These aren't the greatest quality images but they were the best examples I could find. There could also be the variant without armour.
Or they could all be like this ^ with the armour being pieces that you could choose to glue on.
Alternatively, there are the Halo 3 marines which people like more but personally, I prefer the Halo CE design though these are good too. Either way, this has been something I've been wanting badly with weapons that ideally look similar to the Halo assault rifle.