I would have thought that an intermediate "decoupling" board should do the trick. Get your 4 wires, connect the earth wire to a common point, then off to the PSU. each live wire then decouple to the common point via a 1NF disc, 1 MF polycarboante and 100 MF, then feed through a 100 micro H coil to the +3.3V feed. The PCB suppliers have saved a lot of real estate and money by letting you do this.
Should do the trick. If you find you still have a noise problem then you can boost the decoupling for that line.
Frank