So you have an Eevee with perfect IVs in HP, Attack, Defense and Sp. Def and you want an Eeveelution that can make the most of those stats, but also has the shiny form that you like.
Espeon and Glaceon focus on Sp. Atk and Jolteon focuses on Speed, which were the two stats you're lacking the perfect IVs in so maybe it's best not to do them.
I think that since your Eevee has higher Attack, going for Flareon or Leafeon might actually be the best bet, since Vaporeon has high HP but isn't really physical based, and Umbreon won't be able to make use of the increased Attack, nor will Sylveon.
Personally I think an IV spread like this would best suit Flareon or Leafeon, but you could look at each Eeveelution's shiny before you make a decision. Don't want you to feel let down. But if I had to choose the one Eeveelution that best fits your IV spread that doesn't sacrifice much, I'd probably pick Leafeon.