Louis Vuitton does not permit anyone to sell their products online besides their own website so finding a website that's going to get you any miles for the transaction is out of the question.

Saks does often have their EGC (earn gift card) promotion, sort of like a buy more get more type of deal. However, a lot of designer boutiques such as LV, Chanel, Dior "rents" their space (stalls) at department stores, therefore they're not really a part of Saks. Most of the time they are not eligible for those gift cards, though there had been exceptions. Best to find out before pulling the trigger.

The only way I can think of for you to earn miles for a LV bag is to buy the bag with a miles earning credit card, such as Delta Skymiles American Express for example.