I upload my keepass and key file to Dropbox (I know, I know) and then export them to MiniKeePass from the Dropbox app. MiniKeepass auto-associates the key file with the kdbx if it has the same filename as the kdbx, but with a .key extension. I can even edit the DB with Minikeepass and upload it back to Dropbox. It's not as sexy as an Android setup, but it works quite well for me.