It should have been in your UBB zip you downloaded from the Members Area at http://www.infopop.com
If for some reason it went missing and you don't have your original zip, then just head over to http://www.infopop.com and click on the Member Area link in the top right hand corner of the screen and re-download the zip.
Actually, vars_wordlets_mods isn't in the UBB release zip. Check the v2 beta/finished forums for a hack called "Modifcation Wordlets" Its required for some mods.