FYI, there's now a Kickstarter project for the OneRNG entropy generator.
https://www.kickstarter.com/projects/moonbaseotago/onerng-an-open-source-entropy-generator

You can request quantity-of-one for $50 NZD (which is about $46 CDN), or get 5 for $200 NZD.  $90 NZD premium for a hardware programmer.  (It's consciously NOT programmable across the USB interface for safety sake.)

Also quite worthwhile to visit the 'design' site <http://onerng.info/>, which points to both software and hardware 'source code' on GitHub and design materials