It looks like Insurrection Industries is the first online store to begin selling the Sega Triple Bypass board (3BP)! Currently, the ASIC and YM2612 versions are available:
https://insurrectionindustries.com/product/triple-bypass-board-asic-ym3438/
https://insurrectionindustries.com/product/triple-bypass-board-ym2612/
For more information on the 3BP, as well as the newly re-interest of the Genesis 3 can be found here:
http://retrorgb.com/genesistriplebypass.html
http://retrorgb.com/genesis3.html
