@Fargusno Goodfellow's tree-kangaroo should be very distinguishable from tree-kangaroos of West Papua (Grizzled, ursine, dingiso, etc.) just by virtue of them being very obviously heavy brownish-yellow colorations than being dull grey or black.
Goodfellow's tree-kangaroos being endemic to Papua New Guinea makes them seems more unlikely, but not impossible, to be present in any Indonesian collection.