There isn't one that works. There is nothing accomplished by setting an alarm to wake a child if they pee. It makes tons more laundry, it keeps them from getting the sleep they need, a person is not supposed to wake up during the night to go pee, they are not supposed to be making urine during the night when they are asleep.
There is nothing to be accomplished by doing this to your child. He will stay dry when his brain turns on and starts sending that chemical signal the the kidneys to stop producing urine when he falls asleep.
If that chemical is not being produced there is nothing that will make him stay dry at night. Nothing.
If you think about your own body, if you drink tons of stuff in the evening you might wake up due to the urge to pee. But it should not be happening every night, not even once a month.
When you go to sleep you stop making urine, when you wake up and stand up you can feel your bladder filling if you are paying attention. That is what is supposed to happen. You go to sleep and are supposed to sleep all night and not wake up. Then you wake up and feel the urge to eliminate.
You might take kiddo to a pediatric urologist but he's going to say make sure kiddo is not constipated. He may not be getting enough fluids, especially if you are limiting them. Constipation is one of the main reasons for bed wetting outside of the body's readiness. The weight of the feces pushes the urine out of the body when it is laying on the bladder all night.
I think you need to just buy some pull ups and save money. Laundry costs more than a box of pull ups each month. Plus your time is worth something.
Look at some of my other answers on this topic. I have bills laid out so moms can see how much more expensive it can be to add all the laundry in, buying a box of pull ups each month is really cheaper that doing all the laundry.