im pretty sure i fought one on the north beach of sunyshore or in the water north of that...hope this helps!
In Pokemon diamond, Pearl and Platinum you can see the evolved form of Finneon, Lumineon, on Route 223 in a trainer battle. The trainer who has a Lumineon is called Miranda. In Pokemon Platinum the trainer Cassandra also has a Lumineon.
the very first swimmer at the top of sunyshore city before you get to the elite 4 has one
the person near victory roed
Surf north of sunyshore city and one of those swimmer girls has a lumineon.
Yes there are trainers that will have a Combee and a Lumineon, an Aroma Lady in Route 208 has Combee and a Swimmer in Route 223 has Lumineon.
You can find a Finneon at stark Mt. To find a trainer with a Lumineon go to Sunyshore city, and the first trainer you see will have a lumineon at Lv. 38 or so.the 2nd and 3rd fishermen on route 222 have finneon
135 on the Sinnoh dex is Lumineon, you can catch a Finneon with a good rod and evolve it, or you can fight a trainer on route 223 who carries one.
There is a girl swimmer on route 223
Go to Sunnyshore city, and walk north until you reach the beach. Use Surf and the first trainer you encounter is a girl named Miranda swimming back and forth. She has one pokemon, it's Lumineon.
in sunyshore city, surf forward until you see a trainer swimming back and forth. she has lumineon.
It is on route 223 the first trainer you come to she is called swimmer miranda and only has one pokemon, the lumineon if you have the move crunch it faints the pokemon in 2 moves
maybe im not posotively sure but if u know place it up here.=)