Is there a portable way to generate a true random globally unique identifier (guid)?

I am looking for an utility to generate a true random globally unique identifier (guid) in order to copy and paste the generated guid in source code.

Many utilities exist that are based on some built-in guid generator. These generators may include network card MAC addresses, the system clock, pseudo random sequences and more.

The generator must however be true random. This is because of my firm belief that any attempt to reduce the probability of guid collisions will actually increase this probability.