To keep things within your budget and still have decent quality I would recommend using your existing tablet/phone/laptop and subscribe to a streaming karaoke service like Karafun. You'll need some available internet access outside but it doesn't use a lot of data so you don't need to worry if you have to use your mobile data.
The Fifine has a lot of good reviews but I have no personal experience with it. If you wanted to use it I recommend getting one powered speaker like this. I have a similar Rockville powered speaker and it works well.
If you wanted to go with an All-in-one I'd recommend something like this. I don't have personal experience with this either but it does have decent reviews.