Rios are European CIP proof marked shells. Check their web page for service pressure data. Not all will be sub 10,000 psi.
If buying American made, RSTs and Polywads are your best bets for lower pressure loads. But check the manufacturers data for the shells you are buying. These two companies make Saami pressure loads as well.
Many Herters shells are also CIP marked. Again, check the manufacturers data for details on the loads you are looking at before purchase.
Reloading is your best option. 12 ga handloads are easy to keep under 10000 psi with readily available reloading components.
