The link for HyperLynx 8.1.1 is http://supportnet.mentor.com/downloads/index.cfm?id=201009033&product=C101-S117-G111-P10319&redirected=true&reason=0.
Don't worry about the 'Choose Flow' pull-down at the top of the page. It is irrelevant. Everyone downloads the same installation file now, regardless of flow. (PADS customers have the HyperLynx install included in their media.)
For more information, see TechNote mg69591.