Anyone here who has that knowledge should probably not answer your question as it could violate their oath to keep it secret.

Any idiot with a supply of enriched uranium could build a gun-type weapon (Little Boy).

The problem is getting a supply of enriched uranium. Obtaining enough weapons grade uranium (or plutonium for an implosion device) is the biggest obstacle to a nuclear weapons program (besides having every nation on the planet openly being opposed to it).

However, no one makes gun-type weapons anymore. They aren't very efficient nor are they very safe. Fission devices now are implosion type weapons, which require a great deal of engineering skill.