If you want to create a custom linkage for your walker like the Klann variations shown in the video to the right, see customize.
Strider's linkage plans can be found here.
TrotBot's linkage plans can be found here.
Scott Anderson created his own 3D-printed, phone-controlled version of TrotBot - you can find his plans here.
UPDATE: for improved functionality for Mindstorms Strider Ver 3, see these instructions for mounting the EV3 brick higher