I run the Ricky Stator 130W coils for 3 years now with no problems.

Just make sure when you get them they are wound tight and secured with a small zip tie so the winding don't come apart and get caught on anything.

The coils are like $40
http://www.rickystator.com/catalog/suzuki-lt250r-watt-lighting-coils-p-168.html

These should fit the 500 & the 250 I believe