phil001:
To be honset, you wont find a young kitten that has been spayed, don't think this can be done until they are about 6 months- not sure though!
Depending on its age you may have to get its vaccinations done too, again, don't know what age this can be done at.
Maybe do a little research on the internet about the ages that these things need doing.
Good Luck!
Edit - Snap jdeal - beat me to it there!
I just got a kitten recently.....
First vaccination at 9 weeks, Second at 12 weeks.
Spaying at 6 months at the earliest.
Only advice I can give is check everywhere, kittens seem to go quickly at the moment.
Try local advertisement papers, local classified ads, adverts put up in shops, particularly pet shops, websites for local shelters, anything else you can think of.