Found a Source for 10” rear drums with 1-3/4” shoe
It is still interesting that many parts houses don't clearly list this drum. First of all remember that the C-Tek number is for a SBP. So if you have SBP drums, call Centric directly and ask them for a retailer in your area that they ship to. Centric's phone number is in the original post.
I just noticed you're from Canada, I'd still call Centric directly. However, many people have got these drums from RockAuto. You could call RockAuto and insist on that number, regardless of what is posted on their Website.
If you still have trouble, contact me and I'll do some checking on my end. Good luck.