Tank connector is what you are thinking about, but I do not know if they would fit a hose pipe, 15mm would be the size to get if you wanted to try.
I think syphoning is probably best (as Unwashed said).
If you drill some holes near the top that the hose can poke through (make it a tight fit) and then add some cable ties and sealent, then this should help keep the hoses in place, and if the hose is kept below the top of the barrel, then if the syphon is lost it should restart automatically once a barrel is full.