Uninstalling and then reinstalling iTunes should also reinstall Bonjour.
For the reinstall, use an installer downloaded from the Apple website:
... or you could get it back via your Apple Software Update for Windows.
If you'd prefer not to uninstall iTunes, try the following procedure.
Download and save a copy of the iTunesSetup.exe (or iTunes64setup.exe) installer file to your hard drive:
Download and install the free trial version of WinRAR:
Right-click the iTunesSetup.exe (or iTunes64setup.exe), and select "Extract to iTunesSetup" (or "Extract to iTunes64Setup"). WinRAR will expand the contents of the file into a folder called "iTunesSetup" (or "iTunes64Setup").
Go into the folder and doubleclick the Bonjour.msi (or Bonjour64.msi) to do a standalone Bonjour install.
Thank you "b noir". Your "Extract" solution was what I was missing. I had tried "Repair" option for iTunes but that didn't cause bonjour to be reinstalled.
Apple has done an exceedingly poor job of making this solution available. I searched for a long time before finding your contribution.
also, Apple, if you're listening: we wouldn't be so inclined to uninstall bonjour if you wouldn't make it so blabbermouthy in the event logs. Let us turn it off, disable or whatever and then dummy up instead of nagging and complaining that it wants to be on.