Why does everyone always insist on "FREE"? Seriously, some people work so hard on their Android apps, and yet people will still complain if they're not free or if there's ads in them.. This isn't a jab at the OP, but just a general statement..
Back in the days before Smartphones, there was just dumbphones and PCs, and software companies would regularly charge $15-$20 for even simple but useful programs and even more if they were games. These days, if something isn't free in the Play store, people shy away from it altogether. I would think that if you want something GOOD and it's a couple bucks or so and you're going to use it long term, go ahead and buy it. What's a few bucks? A crappy meal at McDonald's?
But back on the direct topic- Go Locker isn't a bad one.. Used it a year or so ago.. Works, but I've heard it's not as good as Widget Locker.