黄金芋, pronounced Ougon-imo here in Okinawa, are a variety of orange sweet potato grown in the Ikei-jima, Uruma area. This potato is related to the famous annou-imo grown in Kagoshima! It is very sweet and creamy. So delicious. It is even better than the American orange sweet potatoes.
Ougon-imo actually were not grown in Okinawa until ~15 years ago when a local farmer decided to try to boost the economy in Ikei-jima! Anyway, they have since become popular.
So if satsuma-imo (yellow sweet potato, purple skin) do not work for your recipes, ougon-imo might be the perfect fit. Look for ougon-imo in farmers markets near Uruma and Okinawa, especially. You might see them elsewhere, but your best bet is always closest to the source.
P.S. Ikei-jima is connected to Okinawa mainland by a bridge, so you can drive there!