You can drive without the rear sway bar, just don't drive too crazy as the handling characteristics will be different.
As for an upgrade, the only one I am away of are the end links that come with an aftermarket sway bar. For example, I have a Progress sway bar and it has end links that attach to a bolt below the hub assemble rather than the strut. Unless you plan on upgrading your rear sway bar then I would just get OEM replacement end links. I think RockAuto has some cheap ones for sale.