I was looking for the same thing at one time. Go to
http://www.whalepumps.com/ . They have them on West Marine's website. I've found a 1 1/2" ID, maybe they have a a 1"ID. You might want to try putting ball valves in your hose line. I ended up doing that with a "T" instead of the "Y". When would sack was full, I would simply close that valve and the other would fill.