Places with good fish-sitters that will take in any type of fish?
There's aquarium services that can come to your house and maintain a fish tank. Expect around 65 to 125 an hour plus expenses and supplies per visit. (Thx @book shelf.) Craigslist, lol, yea, put an ad; "going on vacation, feed my fish, steal my stuff, I'll be back in 2 weeks, here's my keys" Edit I just realized it's a betta. You could hire one for a visit to help you with your bettas recent health issues and see if they'll take him during your trip
you should put an ad on craiglist for it, you nnight find sonneone that way, or have a friend or relative watch thenn