it's not hard only 4 parts.
--------------||---------------------------hot--- (left)
| 2.2 microfarad
from left mic | input capacitor
|
---hot--------+----10k ohm-- "+"
\
---ground----------------------)---+--------------------shield-----
/ |
---hot--------+----10k ohm-- "+" "-"
| resistor 9 volt
from right mic| battery
|
--------------||---------------------------hot--- (right)
2,2 microfarad
input capacitor