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Freshfields has rolled out its arbitration internship programme that lasts for half a year, check that out.

Foreign firms otherwise take vacs, or firms like White & Case have 1-2 month internships. For 6 months, you will just have to search for other places.
Are you willing to pay for the flights, room and board?
If so, then apply where you actually want to visit.

Also do it well in advance as visas in India take forever.

If you are not rich, you need to apply to law firm internship programmes/vacation schemes.
Not sure about internships abroad, but there are firms like Karm Legal that offer internships to Indian students. You can try your luck at such places. All the best!