Counter-pressure filler: can't find the right 3-way valve

[GlowingApple]

I'm building my own counter-pressure filler, and have everything put together but I'm having issues with the 3-way valve. I have a 3-way valve from eBay, and it's the right kind of design, but when I go from closed (handle perpendicular) to open either input (CO2 or beer), some CO2 from the input line bleeds into the beer line or vice versa. It turns out the back of the ball has a flat portion. When that flat portion spans the opening on either side it allows some gas/liquid to bleed around the back of the ball. I thought maybe it was just a low-quality valve, so I looked around at Grainger, but all of the 3-way valves I tried are designed the same.

I can't imagine the commercial counter-pressure fillers have this style of 3-way valve, that leaks when using it, but I can't seem to find out what kind of valve they use. Any ideas of where I can get a 3-way valve that won't leak like this? Worst case I know I can use a T and two one-way valves, but I'd rather have a 3-way valve if I can find one.

 

[GlowingApple]

Finally found one! It's even stainless too! It's 1/4" FNPT, so I had to get different fittings (since I was working with 3/8" before), but it doesn't leak between inputs like all the other valves I tried.

http://www.aliexpress.com/item/304-Stainless-Steel-3-way-Ball-Valve-NPT-1-4-Female-Thread-L-style/32229843129.html

So if anyone else is building a filler and doesn't want to settle for 2 ball valves and a T, give this one a try!