Clock
Bought online from [[http://www.clockabout.com.au]. It is waterproof and glows in the dark. It is mounted to a piece of black acrylic that has been profiled to fit between the rear of the speedo and taco. Weatherproof double sided tape was used to mount the clock to the acrylic which in turn is screwed onto the rear of the instrument cluster.
It works very well and there are many more specific bike clocks available from the clockabout website.
Another option which requires no fabrication of anything is a self-mounting clock from Clocks4Bikes. They have a website at http://www.clocks4bikes.com and an eBay store at http://myworld.ebay.com/ebaymotors/clocks4bikes/ - with the ebay store being the cheaper way to go. They also do clocks to mount to the Stem Bolt for those with ClipOn handlebars. The one pictured has the Temperature item as well - temps can be had in F and C. And they do one with a push button light for night-time time reading. Highly recommended to deal with.