Have a look at the BFU590G device as an alternative to the NE46134 it is a current device and available from Farnell
>>> I just found NE46134 on AliExpress :
I can confirm I purchased a quantity of NE46134 from the above Ali-Express seller and what I received are working fine so I assume they are original devices, they perform exactly the same as the original devices I purchased from RS Components some time ago.
I do have the PCB's for the mixer so please email me direct if you are interested.