Are radioisotope HRNGs commercially available?
This is an old idea:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.110.9725&amp;rep=rep1&amp;type=pdf

I have never seen anybody selling this kind of devices. My assumptions about the reasons:

It contains radioactive material (no matter, was it a capsule from an already approved home appliance or even that appliance "as is") and thus must go through the full inspection &amp; approval process for devices that contain radioactive material to be legally kept for sale.

Every subprocess for the handling of the radioactive capsule also must be approved and have a bunch of certificates.

It's well possible that this device gets its certificate, but the process is far too heavy for a device that is not very often asked in local supermarkets.