Just search for "anti-vibration mount" or "waisted bushing" or "silent block" (or some combination) with your internet search engine.
The original rubber mount is "waisted" (has a narrower waist/central section). The rubber part in the middle is 25mm in diameter and 20mm tall. The studs on both ends have M6 threads and they are something between 10mm and 20mm in length (each).
maybe one of the US suppliers can help with those P/Ns (di Fatta or maybe even APE has a good complete s/h staybar going cheap?)
BTW you will find the rubber silent blok that Edward above pointed out, is also used, is mounted half way up the top part of the stay bar and is the fuel injector rail rubber mount...these are usually starting to split too, so worth checking as now is the time to replace it