This hatchery says they have Welsh Harlequin ducklings shipping now and the minimum order is one duckling…but I would definitely suggest getting two so they can grow up together.
Disclaimer: I know nothing about this hatchery :)
https://www.thechickhatchery.com/product/welsh-harlequin-ducks/...
Most feed stores only sell Peking or Khaki Campbells or sometimes Swedish…I’ve never seen Welsh Harlequin but then again I’ve not been to every feed store! :D
I am sorry you are having to go through this! :hugsDo you have another duck available for your hen? She will be lonely without a companion... Perhaps you could set up a pen with netting for the two to roam in during the day?