I use the Spinlock Mast Pro Harness. You can get these from any well stocked chandlery or buy online. Hope this help
I use a rock climbing harnes… extra padding comes in handy as they are designed for hours of use. Also as there is no mention of the marine industry in the packaging they come in at less than half of the price!
Case in point;
Apologies if this breaches T&Cs – just a simple example….. make up your own mind!