Actually, use the USB MIDI out on your portable grand to control ORGANized. It's a free organ VST that actually does a good job...
It's no hammond or clavia, but it'll give you at least a good overdrive sound. The only downside is having to take around a laptop or your DAW...
besides that, it can be a little difficult to sculpt out a fat gospel style organ on it, but you can get one.
Now before people start bashing me on free VSti's, i know may are crap.....but this is an exception.....it's fairly low CPU, doesn't crash after 30 seconds, but it will ask you for a donation....but you don't have to unless the nag screen really anoys you.