oat milk suppliers

I will be staying at the Shinjuku Washington hotel in a couple of months time & need to purchase 1 litre cartons of oat milk when I arrive. Am enquiring whether there are any supermarkets or other stores that stock it in that area or near by or whether I can purchase it on line & have it delivered to motel.

I've never heard/seen oat milk sold in Japan... Recently rice milk and almond milk are getting recognised but still you cannot find them everywhere. You need to go to organic food shops or special supermarkets handling import food.
Soy milk is very common and you can find them even at convenience stores.

If you need oat milk and other kind of grain milk is not an option, you'll have to either bring it from your home country or buy oatmeal here and make the milk yourself. (All you need is oatmeal, water and portable/small blender which is sold around JPY3,000-4,000.)

In Japan, it is named Oats drink(オーツドリンク）.
http://www.kodawariichiba.com/item/588002604
It seems to have sold at kodawariya(こだわり屋） underground second floor of Shinjuku Halc .
http://www.kodawariichiba.com/shop/shinjuku
http://translation.odakyu-dept.co.jp/LUCODS/ns/tl.cgi/http%3a//www.oda... = en & XMODE = 0 & XPARAM = q, & XCHARSET = Shift_JIS & XPORG =, & XJSID = 0
However, currently, there is a possibility of sold out too many orders.

You could check out Nissin World Delicatessen in Azabujuban.
They have a supermarket full of imported products.
Website nissinham.co.jp.... They speak English. I have purchased rice milk there before.

If I go before this neighborhood supermarket, I found the rice milk and almond milk.
Rice milk had been released from Fukuren and Kikkoman.
Almond milk had been released from the Blue Diamond and Glico.
Maybe, I think that they sell if a big supermarket.
It might have sold in department stores of underground and convenience stores.
Those that are sold in convenience stores, would probably 200ml.
I think Oates drink in the now of the stage, imported goods only been sold with.