What treatment would you recommend to lift/shorten my buttocks? (photos)

I’m not looking to increase the size of my buttocks and I'm happy with the projection of top half, I'd like to address the sagginess of the bottom half (have always had a "long" butt) and cellulite if possible. I was told I'm too thin to harvest fat and that even if I tried a body lift surgery, the lift may not hold for long due to having lots of "weight" in that area, I would like to avoid butt implants. Would Sculptra/Radiesse help me? Which one would be best suited for me? Thanks in advance!