I'm sure it's been done but 2 feet or so of 4" drainpipe, a 2 liter fanta soda bottle, a threaded cleanout fitting with a cap, some rope and some gorilla tape and I have a live bait tube.
I too know the "fun" it can be to have an opened sabiki rig on a kayak! Thanks for sharing your experience.The drag is bothersome at times and its also one more thing in the water tangle a line on or knock against your kayak (noise). I think its usually worth having though b/c live bait is that much more appealing to me (and hopefully to the fish too).
It can be a bit of a rabbits hole, b/c if you have the bait tube then you need a way to catch bait. So now you're dealing with sabikis, maybe a dedicated bait rod, maybe you try the hand line approach, with fewer hooks once you see how absurd a 6 hooks can be on a kayak....
So then there are periods when I just keep it simple and dont even try for bait (and plenty of times I try and dont catch much).
It is still worth having a bait tube in your arsenal though, and its a fun rabbits hole anyways