To convert a non-ABS Swing to ABS would be a financial nightmare. You would need: new wheels, new front and rear brake calipers, ABS modulator, new ECU, different main wiring harness, front and rear speed sensors, instrument panel, front master cylinder, etc
The wiring harness is $365, the ECU is $538, speed sensors $100 each, front brake calliper $300, ABS modulator $860......
I've only listed $2300 in parts. There are many more.
You'd be looking at a minimum of $5000 for parts and labour. I'm also quite confident no mechanic would touch that job, for fear of missing something and the liability involved.
Sell your Swing and buy an ABS model.