Hello Albi,
Probably the easiest way would be to de-solder the laser diode that is in there at the moment and attach a laser at approximately the right wavelength you wish for.
In principle this is not so difficult – what you need to do is look at the schematics/part numbers for Chi.Bio (available on thhis site) to get the part number for the laser diode; then look up the datasheet to see what each of the three “pins” on the diode correspond to, and then find a replacement IR laser with the same “pins” and approximately the same output power.
Off the top of my head there should be quite a few options for laser diodes of ~700-800nm with 5mW power maximum (this is all you need, in fact less is fine) which you could be for $10 or less.
You could then solder in the laser onto the circuit board and use the exact same control circuit and all that which would control it (turn on/off etc).
Hope this makes sense!
.
