How to make SPIP 2.0 template responsive without upgrading

Hi, since we made too many changes to the SPIP 2.0 code it is not possible to upgrade to SPIP 3.0 and make it mobile responsive.
I would like to use current SPIP 3.0 responsive CSS/JS files and integrate them into my template. is this possible ?
if so, where can i find the related JS, CSS files with @media queries etc in the SPIP 3.0 version ?
Thanks