I couldnt get tyres for my KTM in India at all, they are a sllightly awkward size, but Mumbai is definitely the place with bikes and i saw a couple of XTs there so would assume you can get tyres for them in the city, however you wont have a lot of choice as regards make of tyre... there is also a good mechanic in Goa i met, he had an XT and i am sure would help you find tyres, i posted his details in the Repairs Shops section last Jan/Feb time.
In respect of having stuff sent to you while in India, be aware that the customs will open everything and charge you around 100% of its value in import duty before they will release it to you. I made this mistake with some service parts i needed and it turned into a very expensive exercise, they also nicked a couple of things that obviously looked useful to them!!
Hope this helps...
Some day so soon....