What Improvements are Possible for Skewed Lips? (photo)

I am attaching a photo of my lips. To me, they are off-balance on my face and don't appear pleasant. They look the worst when my lips are slightly open directly facing someone. I already went to one plastic surgeon who did an injection of botox on the lower right area of my lip to try and lift up the lips on the right side, but it did not produce the desired result. I'm looking for something relatively non-invasive, simple, lasts for a while, and economical. What are my options? Thank you.