Biomedical Synthetic Flesh

While biomedical gel is fantastic as encouraging most species natural regeneration, there are limitations such as the regrowing of limbs and replacing of many organs. This is where Biomedical Synthetic Flesh is used. Is is similar to a tissue of stem cells that is grafted on and begins to adapt to the hosts genetic structure, eventually adopting the host's genetics almost entirely, leaving only trace markers of its use.
This flesh is not used widely due to many species stigma of using it. Many report the sensation of extra limbs or tentacles during the month long grafting process. Others report having disturbing dreams and visions. Humans in particular often retain the sensation of an extra appendage or two for years if not their entire lifespan.
It is specific to The Grettin though it works well on most carbon based life forms. It also is not susceptible to the Heptil Virus like biomedical gel. 
Created in a series of vats, this unnaturally pink gel glows with a faint bioluminescence that pulses in almost maddening randomness. The Grettin are open to selling the flesh but it must be carefully maintained if it is desired to be kept for more than a few months. This makes it less shelf stable than biomedical gel or stim-sticks which in some forms can last for a hundred years and still be usable.
In the worlds of the Gret Consortium about one in ten Healing Spas will also provide treatments using synthetic flesh. Some less reputable locations will also perform cosmetic modification using the synthetic flesh, some of which includes gene therapies to perform unusual procedures to add gills to air breathers, extra arms or tentacles to others. This modifications are outlawed due to cultural backlash the Consortium has faced, but are still available on the black market.