EndDash
enddash.com
enddash.com
Knockout and Ractive each give you much the same thing at only 40k and 32k and without the dependencies.
We're also in the process of getting rid of those as hard dependencies (jquery, underscore, backbone).
EDIT: Those figures for knockout and ractive include gziping. GZIPed end-dash is only 10k.
There a bunch of two-way-binding plugins for Backbone, if that sort of thing is your cup of tea — and some of them are really well done. Apart from EndDash, some of my favorites are:
Stickit: http://nytimes.github.io/backbone.stickit/
Rivets.js: http://rivetsjs.com
component/reactive: https://github.com/component/reactive