Anyone can build an INS file. All you need is the instrument mappings, instrument names, LSB, and MSB and you can create the text file and save it as a .ins file.
Find one that has been made for another instrument and open it up in an editor and look at the format. Unless i'm mistaken, it's pretty straightforward.
Pa4x - LD Systems Maui 28 - Mackie Thumps