Can anyone give me some ideas how to install a light bar on my zforce 800. With the battery back by the rear wheel I don't know where to get power from.

I used a light bar with movable mounts.  I simply removed the 2 bolts that hold the front of the roof down and inserted the light bar mounts.  I used power from the winch contactor behind the glove box.  A Daystar switch off of ebay is a perfect match for the CFMoto dash.  Please remember to use a fuse and a preferably a relay.  Even though the switch was good for 20 AMP DC I felt more comfortable with a relay.

[2015 Z Force 800 53/Trail EPS]

I just used some bar clamps under the front side of the roof for my 24". Made some special brackets to keep it low. Because it only pulled 4.6 amps I just powered it off the accessory circuit which is already fused. Any more and it's a good idea to run a relay. Had a custom rocker made because I also have a 7" as a rear light. There's pics around here...somewhere...lol

I bought a 28 inch light bar and wiring harness from Amazon.com. Total cost for the 2 items was around $60. A 30 inch bar would be better, I had to drill holes in the roof to mount mine. With a 30 inch you should be able to use the front bolts that hold the roof.
I ran the wiring harness from the battery through the plastic running board to a rocker switch in the panel, then wire tied the wire up the roll cage to the light bar.