From this thread, it's not clear what exactly you need this laser to do and under what conditions it will be operating.
If you need it to run for a couple minutes at or near 25C ambient temperature, passive cooling should be fine.
In your first post, you mention that you have a spare host for a 25 mm module. Is it spacious enough that it can be bored out to 26 mm and accommodate the 10 cm length of the PGL-H1? Can it be modified to attach a fan, and what space is available for a driver?
It doesn't need to run for long, can be operated within a duty cycle.
I had got the impression that these high power modules from cni get way too hot for even a small duration of usage with passive cooling.
That host has extra wiggle room for the 26 mm diameter but is way too short for the PGL-H1 module.
I'll need to get someone to manufacture one for sure.
Years ago I had a few CNI lasers. One was 532 nm and the build was similar to the Laserglow Aries. It was rated for 400 mW and produced over 800 mW peak and averaged 600 - 700 mW depending on ambient temperature. It's been a long time, so I don't remember exactly but from a cold start at room temp, it took about 30 seconds to reach peak, then slowly dropped over time. I don't think I would run it longer than 2 minutes or so except on cold winter days. The laser was based on the PGL-H module (shorter, brass). If the 800 mW PGL-H1 is similar, I'd expect that you can get short runs like this with just passive cooling. I'm not necessarily making any suggestion here, just trying to give you some context for what you can expect based on my past experience with a similar laser.
I dug up the thread in case you want to see more on this particular laser. Photos and videos are mostly expired, sorry about the quality from about 14 years ago...
We used to have a bunch of machinists around here. Unfortunately they seem to have vanished over the years.