Hi tlevine,

Yes you are right you cannot connect microphone directly into the LR-16.
There are couple of cheap preamp on the market, what can be enough for you in this situation.
There are couple of preamp from the cheap one to more expensive one:
Multi channel preamps also available if needed.
You also need to take care with the LR-16 input connection, because the inputs designed for the insert syle connection where the TRS (jack) inputs following this pinout:
T (tip) input signal from your source to LR-16
R (ring) return signal from the LR-16 to the insert connector
S : Common ground

If you want to use the device without insert connection (I think that’s your case) you need to leave the R (ring) pin disconnected.

The ebay link in your post are a speaker amplifier. That’s not solution for your problem.