I bought 5/16" stainless square bar stock from Mcmaster.com (8986K13). Cut to the desired length and use the original bar as a template - clamp it centered to the new bar and drill the two holes through the original holes. A 7/32" drill ought to work.
Thanks. I’ve always been happy with my orders from McMaster-Carr. I went ahead and ordered myself a 2’ bar just in case I ever need it.
I believe the most recent version W.E. square bar has 3 holes through it. One pair of symmetrical holes on the outside from the center and a third single hole offset to the left from the center. This single center-offset hole is for the standard vise model you use, Bob. Three holes insure that the one square bar is compatible with the WE110, WE120 and WE130 models, and all the upgrade kits with their attachments or installations methods.
If you’re going to upgrade or modify your set-up with this new longer square bar, you may want to drill the three holes to make it compatible/backwards compatible with every W.E. model so your covered if you should choose to upgrade your set-up’s vise in the future.