You now have a third choice of operational amplifiers for the Muffsy Phono Preamp, the NJM2068D from New Japan Radio (datasheet, pdf).
The NJM2068D is a great op amp that sits between the NE5532 and OPA2134 performance wise. It draws less current, so it will be the best choice for battery powered Muffsys.
It's available as an option for the Muffsy Phono Preamp on Tindie now, at no added cost.