Can somebody recommend a mono mixer capable of handling a headset microphone input and an audio input from a phone - have a mate who wants to run a mobile pirate talk show with a "throw-away" sim or phone. The mixer is to preferably have an output impedance of around 5 Kiloohms and output level of around 200 mV RMS. Thanks, Mike

Why don't you build something yourself? It's simple enough, and you'd get months of use from a 9V battery. The whole thing would only need a quad op-amp, a few resistors, a couple of pots, the connectors, and a little box to put it all in!