I x-ref'd the Kubota to wix and came up with filter #51365. I'm guessing NAPA sells them, which is MUCH closer than my closest Kubota dealer. What oil do you use in yours?
A local auto parts or NAPA will have a quality Wix or Hastings oil filter for your BX. Of course, Frams are sold everywhere, though most dislike them.
As for engine oil, I presently have Kubota 10w-30 but will be changing soon to Shell Rotella T. Either 10w-30 Silver jug, or blue jug 5w-40 from WalMart.