After months of waiting eagerly it looks like they're popping up. First sighting I saw was on ebay the seller said they found it at a shop in Mexico. following weeks a few more have shown up on site, they are still pretty dang rare, I've seen them bid war up to 80.00 USD and is the average going rate.
Talked to my local walmart's Hodor (chill dude in charge of toys) and says his halo mega bloks are all going off shelves in 3 weeks and in 4-5 all new ones are coming to the store. Assuming with this they'll be more available worldwide by mid or late August.
Haven't gotten mine yet, but I personally am exciting to get my hands on a set. Happy hunting to everyone else!