You're right about needing to breed in order to get an Eevee with Wish, but since no Pokémon in the Field egg group learn Wish by levelling up it will be a little more complicated. The easiest solution would be with the event Pichu on the roof in the Onyx Ward (or the Fennekin in the WTC if you've reached there yet) which has a chance to know Wish when you get it, allowing you to soft reset until get one (preferably a male) that knows it. If you've already gotten these but taught them new moves, I believe you can get egg moves back at the move relearner in this game so you can check if Wish is in those lists. Now if you've already gotten both of these/aren't at the WTC yet and you didn't get Wish, then you're still fine, you'll just need to get a male from a different egg group that knows Wish (in this case probably Fairy, such as Swirlix or Togetic) and a female that's in both Field and the other group (like Pikachu, Togedemaru, or Skitty), and breed their male offspring with a female Eevee so the offspring learns Wish and then evolve that into an Umbreon.
Sorry that I got a little carried away there, so TLDR for the simplest ways to get a Wish Eevee:
-If you've gotten your 13th badge, get to the Fennekin in the WTC and soft reset it until you get a male with Wish,
-Otherwise, if possible, get the event Pichu on the Onyx rooftop and soft reset until you get a male with Wish and then evolve it into Pikachu,
-Or if you can't do either, get a male Swirlix from the Sweet Kiss Candy Shop, level it up to 45 so it learns Wish, and breed it with a female Togedemaru so you get a male Togedmaru offspring,
Then breed the outcome of one of those with a Female Eevee/Eeveelution.
Thankfully Foul Play is a lot simpler to get, since you only need to use a tutor for it. However that tutor is only available in the Peridot Ward once you get your 14th badge, so I guess you'll be able to get Fennekin by then anyway. Hope I didn't overcomplicate this and good luck!