I just used some left over RO tubing that I had. put it under a 10 gallon aquarium that i had to falten it out some and then just used a JG fitting to connect it to the 1/4 tubing I already had. seems like it will work out well.
I know this topic is old as dirt, but I too was/am looking for 1/4" OD rigid tubing. I stick it down into my top off reservoir and my cal/alk dosing jugs. Regular RO tubing works, but it does coil up a bit. Even if you heat it a little and try to bend it in the opposite direction, it still wants to coil up. It's hard to get the end of the tube to stay at the bottom of the jugs.
Anyway, just thought I'd mention that Lee's Pet Products 3/16" rigid tubing slides right into a small piece of RO tubing, which then can connect to quick disconnects, etc or what have ya. Essentially just using an inch long RO tube as an adapter. It's small stuff, but it works.