I put out a call on the rescue ducks group page.
I found a number of potential leads on line.
https://www.birdsnow.com/login.htm arranges adoptions and takes enquiries from Canada.
Woodlands Wildlife Sanctuary in Ontario might offer advice if they don't adopt out ducks [they don't talk about duck adoptions]. They may be able to tell you which if any organizations or rehabbers take in domestic ducks.
Flying Hope arranges adoptions for companion birds [aka pets]. They likely mean parrots and parakeets, but contact them and ask!
https://flyinghope.weebly.com/
Similarly, cherished wings is parots and birds -- but contact hem and ask
https://cherishedwings.ca/contact-us
Another search came up with:
https://www.ontariowildliferescue.ca/wildlifecentres/?care=bird these are for wildlife but domestic ducks get abandoned on ponds and in parks, so contact them all and ask!
https://www.ontario.ca/page/rescue-sick-injured-or-abandoned-wild-animal ask them which rehabbers might havre taken in abandoned ducks. I don;t know your situation in Canada but in FLrida where I live, it is illegal for wildlife rehabbers to take in muscovy and many wont take abandoned domestic ducks as they cannto release them to the wild. But there are persons who the rehabbers know who take in muscovy and domestic ducks. If asked they will tell if they think the enquiry is genuine
https://www.ontario.ca/page/find-wildlife-rehabilitator
Ottawa Valley Wild Bird Care Centre, Nepean, ON
Located within the Stony Swamp Conservation Area, the
Wild Bird Care Centre takes in around 3,000 birds annually, all of them brought to the centre by caring citizens. With a resource centre — complete with observation windows — it’s also open to the public daily from noon until 3pm.
Ontario SPCA website has a section:
Animals Available for Adoption through our Community Partners
lastly:
https://eriewildliferescue.ca/