As an alternative to spending more money, you could try a free vocal plugin named GSNAP (search for it on google)

I don't think it adds harmonies, but it WOULD help to keep individual harmony tracks on pitch. In other words, you can add harmonies by singing a harmony part (or two. Or three) Then if they are not perfectly in tune, use GSNAP to fix them . There are advantages to using this approach:

1) there will be slight variations between timing of the parts, which will make it sound more like multiple backup singers (whereas automated harmonies can sound "too perfect" or programmed)

2) you can put each part on a separate track and tweak them individually

3) if you make a mistake you only have to redo the one part. With auto-harmonizers you end up doing it all at once, so one mistake invalidates the whole enchilada

4) its free

5) Automated harmonies require a real learning curve to get the harmony I want (and there are MANY variations on harmonies.. very frustrating to pick a preset that gets all the notes right, but one). If you go the route of actually singing your own harmony, you can get it the way you hear it in your head the first time. I have literally wasted days trying to find the right harmony in TC Helicon's list of presets. In some cases, I've given up entirely.

https://www.dropbox.com/sh/ey71h8ep047758h/AAC12jNM0Hz9Q8zsh5iDeqNHa?dl=0