Hey I'm looking for a rear seat cowl so I can covert my bike to a solo to save on rego.
Does anyone have one? I live in Aus

I assume you are in Qld. Where are you?
I have made one but it requires the actual seatrear and  foam to be removed.
Pretty easy to make a fibreglass one to go over the back useing the seat itseal as a male mold. Fair bit of finishing work but you can get quite good results that way. Did it for a while for proddy racers with "same shape and size rules".

Yeah I'm in Brisbane QLD. I'm after one that can just go over the seat so that it doesn't need to be removed.

There's no longer a requirement for an inspection. You just fill in the form and take it to your local transport office. Just take off the rear pegs, no ones going to measure your seat.