Mefloquine (tradename Lariam) is easily available at medical stores as well as Malarone is available at least in some places is India (e.g. Connaught Place in Mumbai). Or maybe you catch a foreign traveller with extra to sell.
But I wouln't recommend Mefloquine (Lariam) as antimalarial medicine, because there is controversy over it. Since its introduction, it has been directly linked to serious psychological side-effects including depression, anxiety, panic attacks, confusion, hallucinations, bizarre dreams, nausea, vomiting, sores and homicidal and suicidal thoughts. Malarone has the fewest reported side effects and it's which is much more recommended in preventing and treating Malaria.
But you can try to buy Malarone before you go to India, in any pharmacy (even in some Tesco's). It is better to buy them in advance by making the appointment with your doctor. If you can't, you may try to buy it on-line, there are several online pharmacies such as Total Pharmacy, Express Pharmacy, Travel Pharm, etc. After that usually you need to send your prescription via post. Please note that some fraudulent online pharmacies may attempt to sell an illegal generic version of Malarone. These medications may be counterfeit and potentially unsafe.