Lux 5.0 or any other halo mod are just replacement bulbs. You can search in the vendor classified section for them or buy from an online store such as JleviSW.com bavauto.com or bimmian.com among many others. You can also look for them on eBay.
If you want blue you might want to look at RD angle eyes, they make a bright blue variant. Try the sponsor section or Bimmian.com first for those.
EDIT: MForce sells the RD's here
http://www.e90post.com/forums/showthread.php?t=275370