I import almost all my bettas. I live about 30 minuets away from Linda Olson so it's very easy for me to pick up my bettas.
is a good source as well.
Keep in mind that few US sellers offer nice fish for reasonable prices. I saw a pair of dragons up for $75! The fish were worth maybe $10 in my eyes. Join the IBC, read the standards, and choose very wisely.
Basement Bettas or Martinismommy have some of the best fish right now.