You're suggesting that embryonic tissue has kidneys that might be sold on the black market for transplantation into a human? Or into another unborn embryo?

Kidney start working as in producing urine at about 13 weeks, which is already second trimester. So you wouldn't usually get an abortion that late, even in California.

Furthermore a 13 week old embryo is a little under 3 inches long, and the kidney is less than 5/12ths of an inch, whereas a human kidney is about 5 inches long.

So you wouldn't be able to sell it on the black market, as the surgeon will immediately spot that its nowhere near big enough to transplant into a human, as it will be about 1/12 of the length and about 1/1700 the weight of a kidney.

But you know this already, don't you?