I wouldn't spend too much. I suspect you will be quickly advancing to a significantly more expensive turntable/tonearm/cartridge if the rest of your system is any indication.
With that in mind, I have found the Benz Micro Ace moving coil cartridge to mate well with the SL12xx. Otherwise, I'd look into an Audio Technica AT150Mlx if you'd rather have a moving magnet cartridge.
With that in mind, I have found the Benz Micro Ace moving coil cartridge to mate well with the SL12xx. Otherwise, I'd look into an Audio Technica AT150Mlx if you'd rather have a moving magnet cartridge.