how to get a vaporeon after using the name trick..

The only thing you can do is to pray for your luck and hit the EVOLVE button. :)

http://www.eurogamer.net/articles/2017-08-01-pokemon-go-eevee-evolution-how-to-evolve-eevee-into-vaporeon-jolteon-and-flareon

Rainer

Just press the button and evolve it. 33.33% chance.
Flareon and Jolteon aren't bad either.
If you want to be safe, go for Espeon by buddying and walking 10 km.
EDIT: Whoever downvoted, which part of my post are you disagreeing with?

You want a high IV Vape? Do some Vaporeon raids!
Too much RNG when just evolving and you'll prolly get a Jolteon.. jikes

You may want to use this 100% eevee and turn it into an Espeon?..

I asked the same question some months back when I got my 100 IV Eevee. Of course while I didn't need another Vaporeon, I was thinking about making it a Espeon (this was before the gym rework). But I decided to keep my perfect eevee just like the way he is till Sylveon, Glaceon, or Leafeon are released.

A bit of a wait for sure, but its not like keeping one eevee is going to bust my bag. Heck, got a 100 IV Marowak and Aipom that I would dump first instead of that eevee.

Mukun, what I would do In your situation is hold onto that eevee until a year or so (lol, hopefully!) when gen 4 releases to obtain glaceon or leafeon, or gen6's sylveon.

In terms of obtaining a good vaporeon, as others have mentioned, there's a 2/3 chance of NOT obtaining vape :(

What you could do to attempt to get a good vaporeon, if desperate, is either gamble and roll on that eevee OR go after vaporeon raids and hope for the best