Hello Chris
If you have a laptop or your keyboard is by your computer, then try the B4 Soft synth from Native Instruments, http://www.native-instruments.com/index.php?id=b4ii_us which is as near as you can get to the Real B3. (A Demo version can also be downloaded)
Also have a look to see if you can find a Wersi OX7 Expander, as this has emulations of the B3, H100, Helios/Galaxy and Spectra Organs.
Hope this helps.

Bill