You would need to specify your location to know which is nearest. I live near Sacramento, CA, and the nearest to me in in Carlsbad, CA.
At your nearest Lego store or Walmart.
Sadly Lego costumes do not exist, however you can buy weapons etc. from your nearest Lego store.
Sacramento
Well, the nearest Legoland is at Windsor, however there is a Lego Discovery Centre at the Trafford Centre, near Manchester.
join a club first... then ask someone in the club when the meetings are... you can find the nearest club by going to your nearest Lego store and asking them about local clubs or calling them on the phone... if you now longer a kid.. then you are considered an AFOL (ADULT FAN OF LEGO).. Google it..
Some of the main attractions are Disney World, Lego Land, Sea World, and Universal Studios.
Station 9 3/4
Amazon.com has "Lego Studios Jurassic Park Raptor Rumble Studio 154 Pieces Ages 7-16" - product number ASIN: B00185OBZQ .Also , try www.lego.com or www.shoppingedge.com
The best way to purchase a Lego Star Wars set is to visit the nearest shop where they sell toys for children. You can also try your local supermarket or order it online on vendor sites or the site of the nearest shop for children's toys.
A good online Lego shop that I have heard of is the online shop. Find the website at: www.LEGOshop.com Except for the online shop, there are actual local shop limited to some countries.
studios
Disney's Hollywood Studios was originally called MGM Studios, but is now called Hollywood Studios, it is nothing to do with Universal :)