A week later, I heard back:
> [...] The product or particular concern that you describe does not fall within CPSC’s jurisdiction. You may wish to contact the agencies listed below, which we believe can best handle your concern.
> U.S. Food and Drug Administration Center for Devices and Radiological Health Document Control Center – WO66-G609 10903 New Hampshire Avenue Silver Spring, MD 20993-0002
> https://www.fda.gov/radiation-emitting-products/getting-radi... [...]
(BTW, I suspect the process apparently not forwarding a report between two agencies will result in some problems falling through the cracks. And it did, in this case, since I stopped holding the defective unit (I'd asked in my report that they let me know if they wanted to examine it), returned it to the store, and never looked into starting over the reporting process with a different agency.)