Lab Grown

PRP is widely available now. Sometimes branded under the trade name Priapus Shot or P-Shot. It just hasn't delivered consistent penis enlargement so it doesn't attract much attention.

Now they're promoting PRP as a possible ED treatment that might work in 24 hours, or maybe after 3 more treatments, or maybe after 4 months. Or it might be promoted to rejuvenate the penis, promote healing, or to restore blood flow.
 
It's probably not a high priority. I think most plastic surgeons are more concerned with transplants for accident victims and veterans.

There has been some slow progress with skin grafts, but the entire penis is a more complex organ.

I don't think anyone has found a way to isolate penis growth from the other hormonal effects of puberty-adolescence – whoever cracks it will become a billionaire:

When Does Your Penis Stop Growing?