Well David that sounds like an uncomfortable problem, my advice, for what it's worth, is to go to your nearest seat refinisher and see what they can offer, the only problem with custom seats is they cost a bloody fortune and getting it right can be a bit hit and miss. If gel pads don't work then how about a seat cut out like they do for horse saddles, I know it sounds daft but when you think about it your pain comes from resting your tail bone on the seat itself, if you can reduce that or even eliminate it then you should have a more comfortable ride. something like this might help?
from these people http://yamabits.co.uk/yamaha-mt-07-comfort-seat.html
Good luck with your problem mate, this is £176 so not cheap. I know it's not for your bike but I bet they will make you one.