We are trying to get ungated for Nike in Canada

However, we are having difficulty finding suppliers/retailers that provide official invoices and not receipts.

We tried Footlocker and SportsExperts and both of them offer only receipts.

Any luck from fellow Canadians?

Not only receipts, make sure you have written permission from Nike too allowing you to sell their brand on Amazon. They can take your listing down anyday.

Nike won’t give you the permission to sell their products even if Amazon allows you to do so you. You have to be an authorized distributor of Nike to sell your stuff as new. You can sell it in Used condition. A brand can request Amazon to take out unauthorized listings.