It's down at the moment until the Gentoo devs can sort out a security flaw, but the online Gentoo packages database Web page (
http://packages.gentoo.org/) will be back online at some point in the future. When it is, one can use wildcards in the search box, such as "*-bin" to find binary packages (all have the "-bin" suffix, as
wolfden stated) in the Gentoo repository. Having found a binary package -- and there aren't that many -- you emerge them as
wolfden has described. Mind you, if one is using Kuroo one can use part words to search, so one could find any binary packages in the Portage tree that way too. (I'm not on my SL PC at the moment, so cannot check if is also the case for Portato, but someone will no doubt confirm if it is.)