Where can I get Bagon and Trapinch..?

You get Bagon in meteor falls in a special small room with a tm in it.
And Bagon evolves at 30 and 45-55
I think you find trapinch in the desert and it evolves at 30 and 45-55

Bagon may be obtained in Meteor Falls after you have HM07-Waterfall. There's a small room you will be able to access by going up and down the correct ladders, then surfing a bit to get to the ladder up to that room. That's the only place you can get them at,and it may take a little while, but it's worth the trip! He'll evolve at Lv. 30 to Shelgon, then Lv. 55 to Salamence. But if you keep him a Shelgon, he'll get all moves by Lv. 53, then evolve(or it'll be Lv. 93! B/f he gets his last move)and won't miss any moves, either, by doing it that way.
A Trapinch can be easily obtained in the desert area-Route 111(get the Go-goggles in Lavaridge 1st so you can see!) He'll evolve at Lv. 35 to Vibrava, then Lv. 45 to Flygon. He'll get different moves (like Dig)if you keep him a Trapinch(only Ground-type, not Dragon, too) than if you let him become a Vibrava/Flygon(they get the same, just 2 moves at later levels for Flygon-Sandstorm & Hyperbeam)
Hope this help in creating a few BAD@$$ Dragons for your game! Good Luck!!

Bagon can be found all the way back in a small room in Meteor Falls; when you encounter it Bagon's level will be between level 25-35; it's next evolution takes place at level 30 which is Shelgon, then it's final evolution stage which is level 50 which is a Salamence by then. Trapinch are very easy to locate they can be found in the Desert Ruins on Route 111; this Pokemon evolves into a Vibrava at level 35. Vibrava then evolves into a Flygon at level 45.

To catch Bagon go to Meteor Falls and it's on the platform where you surf to get Dragon Claw. I don't know when it evolves to a Shelgon. To get Trapinch go to the desert near Lavaridge townand search for it. It evolves at level 35 to Virbrava amd 45 to Flygon! Good luck.

I don't know about Bagon but you catch trapinch in the desert

You get Bagon in the cave that you get Solrock. You have to climb the waterfall though. Then you have to look for a really tiny cave inside of the cave that you are in. Then use surf in the little cave and go all the way up and you will find Bagon. Bagon evolves at level 36 if you get a level 35 Bagon into Shelgon and Shelgon evolves at level 56. You get trapinch in the dessert. It evolves at level into Fly gon at level 45 for it's final stage.

Meteor Falls= Bagon Desert= Trapinch