Just use a big board that has some tie downs points. I use a Sunova One 10'1 x 34" and 203 litres. It's very stable...in calm waters, I can cast a saltwater fly rod off it. Starboard have big touring board with tie down points in front and back

For your gear either a waterproof backpack or a milk crate tied down up front. You can lash key items to the milk crate and/or attach a rod holder. If you're keen on an esky, you need a board with rear tie down points or you can use roof rack straps and run them around the bottom of the board (creates a bit of extra drag, but with all the weight you aren't moving very fast anyway).

Has anyone owned or know anything about the Jp Outback SUP..which seems like it is a fishing SUP...are they available in Australia?
thanks