Contact DIT. They'll send you a list a qualifications. You send your doc**ents to them for revue. For a fee they will write you a letter stating that you qualify for HSE status. Then send that and your doc**ents to the Canadian Board of Diver Certification. For a fee they will certify you and you'll have your HSE diver card. HSE is IMCA recognized. You will also need some other stuff, such as OPITO, Passport, and such. Check with Compass personnel services for what else you might need.
By the way, you will need to have logged Dry Suit dives. Something that most GOM divers don't have. The best way to get the Dry Suit dives that you might need is to work for a Potable water company for a few months.
Your other option might be to go to that school in South Africa, that's the cheapest school in the world that is recognized by IMCA. You can Google all the contact info. Good luck.
You might also check out the school in Jacsonville that has an advert on this website. They run multiple a****sment programs and their DCBC certification is IMCA recognized. I read their training a****sment on this website on another thread and it looks like they will cutom taylor the training you will need.