I googled around for a while and mostly found information on what should be in pond potting soil ie some mix of sand/clay/loam + fertilizer.
I was really just looking for some off the shelf product to use in some cloth pots to use in a container pond. The only aquatic specific products I found were really expensive as they were aquarium substrate. Such as:
Pond Care Aquatic Media
All the usual aquarium substrate Ecocomplete, etc, etc.
I'd have thought there would be something more cost effective to use in bulk for ponds.
Don't ask for advice. Ask for information, gather lots of information from different reliable sources. Then use the information to make your own advice.