I think they are not available cause they do have problems with them from time to time.
A big importer who is suppose to be a leader in the industry, brought some thousands of Pohnppei clams, apparantly, most of the clams, if not ALL died.
When you have such loss, it makes one think if Pohnpei clams are worth importing, they do have bright colors, but they do get some kinds of virus/bacteria from time to time that also attacks other clams in the system.
Also collection methods of Pohnperi clams are sometimes the issue.
Bottom line: risky.