I think retro-fitting ABS would be a big job. In addition to the obvious components (rings on brake rotors, sensors, two large ABS pumps, mounting brackets for pumps and sensors, different footpeg plates, etc.), you'd need an ABS wiring harness so you could plug in the ABS brain. If you really want ABS, I think you'd be better off selling that bike and buying a different one with functional ABS.
But if that sort of project appeals to you, I have a complete ABS system that I removed from a 1992 K75s - would be glad to sell it all in one go. It may or may not be compatible (although I'm sure the wiring harness is NOT compatible with the 4-cylinder bikes).