I've been using the Prolimit race vest (don't be fooled by its name) for the past 10+ years and have always found it the perfect combo of good impact protection and floatation. It doesn't get in the way whilst sailing and it has a back pocket for my PLB.
It technically won't comply as a PFD, but it surely looks similar if you know what I mean.
The foam is nice and thick, it saved me from a foil tip puncture on the back last season.
The strap prevents it from sliding up. I'm using a waist harness.
My first one lasted nearly 10 years, the replacement I got at the beginning of this season already has a broken pocket unfortunately. So not sure if I can still recommend it, quality certainly got worse.
Looks like Patrik have a very similar product that is possibly more easily available in Australia, although can't tell if the padding is as thick based on a photo only.
www.prolimit.com/products/402-43000-weight-race-vestwww.surfsailaustralia.com.au/product/patrik-windsurfing-speed-weight-vest