Potentiometer identificaiton Logitech z623 Speaker
Six pins means that it's a &quot;stereo&quot; pot, with two independent potentiometers that are ganged together mechanically.  These are almost universally arranged so that the center pin of each set of three is the pot tap, with the two outer pins being the ends of the resistive element.  The &quot;A104&quot; almost certainly means it's a 100k-ohm pot (&quot;104&quot; on an electronic component usually means \$10 \cdot 10^4\$ of whatever units of measure are important -- in this case ohms).
Beyond that, get on to the website of an electronics supplier in your country (DigiKey or Mouser in the US, Farnel in Europe, I can't help you outside of that).  Look for a 100k-ohm audio taper pot that has the same exterior dimensions as the one you have.  Be sure to get the shaft size right.  Cross your fingers, order a few, and try them out.
There's a chance that you won't find the exact thing you want, especially the details of the shaft length and dimensions of the &quot;D&quot;.  This is because Logitech will have made enough copies of that speaker that they can economically special-order the pot to whatever specifications they want.  So you may need to get something that'll fit the board and bodge the knob mounts a bit.