https://www.ebay.com/itm/325232750362
I wouldn't really recommend it, however, as I confirmed you can't use a virtual memory card with the snac port for that controller enabled. It still works for the second port that isn't snac enabled, but some games don't like saving to the second card even on real systems.
From the wiki:
SNAC can be selected for each port and will support gamepads and memory cards on the corresponding slot. When SNAC is enabled for a slot, the emulated gamepad/memory for this slot is disconnected.