You can go to
www.sun.com and download a version of Solaris 8 for Intel machines. They still got the link there i think. Or you could order a set of CD's from the site. About $100 (I think).
If you want UNIX and on a Intel that is the best way. I assume you mean on a Intel based PC.
Or you can purchase a second hand Sun box from places like ebay.com and some come with the OS. or purchase the software on it's own.
Or (as said before) you could use Linux. Not that much difference. Well there is, but basic's are the same.
With what I have said above I assume you want Solaris flavor of Unix.
To be able to help, we really need to know;
- What flavor of Unix?
- What platform you want to run it on?