Local game store sells Tomee and Yobo brands. Both worked when I had them hook my model 1 Genesis up to check that it actually worked.

https://www.amazon.com/gp/aw/d/B00KYM4AH8/ref=mp_s_a_1_7?ie=UTF8&qid=1512962963&sr=8-7&pi=AC_SX236_SY340_FMwebp_QL65&keywords=sega+genesis+1+av+cable