Making your own oriole nectar is easy.
Just mix 1 part sugar to 6 parts of water. You'll need to heat the mixture to disolve the sugar completely. Then let it cool. Once your solution is cool, you can put it into your oriole nectar bird feeders.
Barn in the Sticks has a nectar pot, which can be used to heat and store nectar.
You'll see orioles really hitting your nectar feeder for a quick energy boost when they return from their migration flights. Then keep them coming with oranges and jelly. Orioles will only nest near a food supply, so keep the nectar, oranges and jelly out to keep encouraging the orioles to nest nearby.