I use a laptop. You can use Word or a free word processor. I like that you can categorize by artist, name, genre, recent...about anything you want.
You can get any size and pay about anything you like, but word processors take very little power. All I use mine for is to display lyric charts, play MP3s on breaks, maybe search the internet occasionally. You can also display PDFs of course. You can zoom the lyric size, etc., very flexible.
Mine is powered by USB so no big power transformer.
You can get one with solid state memory for under $200.! If you need extra memory USB sticks are very inexpensive.