Here's a pic and a brief description. Miks MCS Repairs made what I have so perhaps he'll chime in.
A tube with one flattened end is loosely bolted to the firewall so it can rotate up. There is a spring retainer on the firewall to hold the tube when the cowl is closed. A short piece of smaller diameter tube, again with one end flattened, is attached to the cowl door. When the cowl is opened the longer support tube can be rotated up to capture the short tube on the cowl. The cowl stands open and secure unless the wind is really blowing. Simple and light. Click on the photo to blow it up. I can click it three times and see good detail.
I like using one of those fabric clamps, the kind with the orange pads for your fingers and orange pads so you dont scratch things and clamp both panels together open.
If up for an extended period of time, we just clamp the two together (reminds me of when we used to clip our Labrador's ears over his head to see what he'd do . . .)