I use those yellow Worktunes. I get them at Home Depot for around $50. They seem to last for about a season. The battery cover breaks off, so we use duct tape as the cover. The digital tuner is weak, the old analog tuner was superior. But the digital ones have an input for an mp3 player. Batteries last a couple of weeks.
They are far from perfect, but I have tried some others with even worse results.