[mehrkat]

If it heals you it already exists

Just buy regeneration with regrowth. Regrowth describes the speed and Regrowth gives you the regrowing parts that are separated.

Please note: I find Regrowth to be too expensive in RAW. But by RAW Regrowth and if you want it to be relatively slow (a couple of days total just buy it at the cheapest level of Regeneration 1/12 hrs HP.

If you want it to work more quickly just speed it up with Regeneration.