Very doubtful, it is not as simple as regular Power Steering like on a car etc. Lots of fancy computers and mounting points on the frame. I am sure it would be cheaper to sell you 04 and buy an 07 Foreman with Power Steeing... or wait a year or so until the Rubi has Power Steering.
I will say it is WELL worth it as Honda's Electric Power Steering on the Foreman is very impressive.
