You can get him at the vally windworks on fridays but make sure it's midnight so set time to Thursday 23.55 and just wait 5 mins for it to come there.
he's in mt cornet
On a random day every week, a drifloom appears just outside the factory near Floarama Town
Its drifloom in valley windworks
go to valley windworks in a Friday
In front of the Valley Windworksonly on a Friday
walk in the windmill place for a while then you should be able to find it
Every Friday he will be in front of the valley wind works.
Other than glitches, no, there aren't any.
According to this Serebii page you couldn't get one until Pokemon Diamond and Pearl. http://www.serebii.net/itemdex/shinystone.shtml
Drifloon is a Ghost and Flying type Pokemon introduced in the fourth generation. It can be found outside the Valley Windworks in Pokemon Diamond and Pearl.
I believe that the 6th (I think) Gym leader or at least one of the trainers in her gym has one.
level 28