Buy a new one.
The Baja Doodlebug mini bike has been discontinued. However, you can still get reconditioned ones (as of 8-10-12) at suggested link below.See related link below!
I think you mean where and the answer is in a mini bike store.
One can buy a mini dirt bike from the local bike stores. Sometimes local community auctions also feature variety of mini dirt bikes for very reasonable price.
look on Craigslist Virginia
india
Canadian Tire stores carry Baha 165 mini bikes $599.00 at least the one in Cobourg Ont. does
Often it is possible to buy a mini moto bike at a regular motorcycle salesman. You go to the salesman and ask him for a mini moto bike. Either he has one in his assortment or he asks his delivery man for a catalogue which he can show to you.
You can be any age to buy a mini dirt bike in the UK wether your 6 or 16 you can buy one but you are not allowed to ride one on the road at any age in the UK you would have to take the mini dirt bike to a dirt track and you can book weekly sessions with them so you can go like 3 times a week if you wanted to. So you are allowed to buy a mini dfirt bike at any age you just can't ride it on the road. i hope that's a help.
http://www.minipocketrockets.com/r32-4-stroke-super-pocket-bike/
Ngk you can buy it at auto zone, advanced auto parts, o' reilly
I own one if your talking about the lime green ones they go 35 they are fast little guys but don't buy one for over $160 because that's how much i got mine for brand new from a dealer in Phoenix.