The best way it record them on a camera. I know you can download different still frames of the various bars patterns, but they may not be really correct. For a long time we used the bars included with Avid, then when we started using material from the field classes in the studio we found that the bars were not correct when the tape machine was set up to those bars. After this we just recorded a short clip of camera bars from one of the field cameras and started using them. All the issues went away so I only ever recommend recording the bars out of the camera that you use. If your camera does not produce bars then you will need to get a short clip from someone for you TV system (PAL, NTSC, SECAM), or download one of the still images and insert this into your project.
The closest thing I've found after a lot of searching is this FTP:
The 525 signals is NTSC standard definition and the 625 is PAL standard definition but they do not have SMPTE bars but the more basic 100% bars. Not sure if they are correct but they should be good enough to calibrate the time base corrector on a deck output. I crashed my Lightworks when I tried to import and transcode one of the low rate NTSC videos so I don't know how these look on the scopes.
I guess before we get rid of our SD cameras I better record some bars and store the files away for future use. I only have NTSC cameras and probably wont get to this for at least a month so I can't really help more than the above link.