I mean, just as an attempt to fill some gaps for the shortlist
African Penguin: Magellanic, Humboldt, Galapagos Penguins
Alpine Ibex: Nubian, Spanish, Siberian and Walia Ibex
Arctic/Timber Wolves: There are a ton of Grey Wolf subspecies, plus Red Wolf
Baird's/Malayan Tapirs: Lowland and Mountain Tapir
Bengal/Siberian Tigers: Various other subspecies
Black-tailed Prarie Dog: 4 other prarie dog species
Bornean Orangutan: Smatran and Tapanuli Orangutans
Colombian White-Faces Capuchin: various other Capuchins
Common Ostrich: Somali Ostrich
Cuvier's Dwarf Caiman: Spectacled Caiman
Eurasian Lynx: Bobcat
European Badger: Asian Badger, Japanese Badger
Formosan Black Bear: Other Asian Black Bear subspecies
Gemsbok: Any of the other 3 oryx species
Greater Flamingo: several of the other Flamingo species - Chilean and American best match
Grizzly/Himalayan Brown Bear: Numerous other brown bear subspecies
Japanese Macaque: Numerous other macaque species
Mandrill: Drill
Nile Monitor: Various other Monitor lizard species
North American Beaver: Eurasian Beaver
Reticulated Giraffe: Other Giraffes - Masai would be my vote (giraffe taxonomy is... weird)
West African Lion: Other Lion subspecies/populations
Western Chimpanzee: other chimpanzee subspecies
Western Lowland Gorrilla: Mountain Gorilla, Eastern Lowland Gorrilla, Cross River Gorilla
