The softoppers do not have removable side windows, but the do roll up. This is a bonus for somebody like me who lives in Oregon and doesn't look to the West before leaving home for storm clouds.
Bestop made a top a few years ago but has been out of production for at least 8 years. They use the same snap pattern though as the softopper, softopper actually used a bestop equiped K5 as a template when developing their own design and it is better in just about every way.
Can-bak was the other manufacturer that had a soft top for the 1st Gen K5. They were the only one I know of that had removable side windows, that is probably what you're thinking of. I believe they also had an option for a roof rack, never saw one in person to confirm that for the blazers though.
If you're going to get a softopper get it now, they have been increasing in price over the last few years, apparently they know they have no competition... It is possible to find them on Craigslist but don't hold your breath.