How do I ask for Self Heating Bentos?

Hi All,
My plan is to purchase a beef bento at Matsuri Ekibenya in Tokyo Station. I would like to purchase the self heating ones. How would I ask for them in Japanese? Thanks.

Kanetsu-shiki ekiben is the term for these.

"Kanetsu-shiki no eki-ben wo kudasai"

Store staff knows word "heating" in EN no worry,
but Matsuri is always crowded, so it is quicker to find it yourself.
https://youtu.be/j4wd7sZKh0g
You can see the image of "how to" also words on packages with a string.
http://ekibento.jp/20050116063.jpg
- 加熱式容器 : kanetsu-shiki youki (加熱 kanetsu = heating)
- 加熱機能付容器 : kanetsu kinou-tsuki youki (機能=function, 容器=container)
- アツアツ/あつあつ : Atsu Atsu (hot! hot!)
https://pbs.twimg.com/media/Ct437DxUsAETFCt.jpg
http://livedoor.blogimg.jp/wickie91/imgs/e/5/e50f66eb.jpg
http://livedoor.blogimg.jp/yonemeshi/imgs/9/7/97acff1d.jpg
http://kfm.sakura.ne.jp/piceb/14/odamaguro1zoom.jpg
http://web-japan.org/trends/11_culture/images/l_popd130304.jpg

This is not "beef(牛/牛肉)" one but you can see about real temp of heating.
https://youtu.be/OQAszBAlfdE
In above vid, although it was opening for showing heating system, but please warm it without opening.
44℃(not "F") is the same hottest onsen water, so please don’t touch until heating over about 5 min.

Now, Matsuri web providing regular ekibens lists in EN.
http://www.nre.co.jp.e.yj.hp.transer.com/ekiben/tabid/229/Default.aspx...
(ekibenya "festival" = ekibenya/駅弁屋 Matsuri/祭)
http://livedoor.blogimg.jp/iessi/imgs/e/8/e8dc6e12.jpg

Thank you, everyone. This was very helpful. I've printed this thread out and will take it with me.

I'm curious about the Rescue Foods Beef Bowl. Where would I buy that? I can take a few of those back home with me for souvenirs.

You mean those?
http://global.rakuten.com/en/store/jnl/item/e475490h0000/

You'd have to go to shops that sell "emergency food/supplies" - I am not sure, but some large supermarkets, Tokyu Hands, or maybe Don Quijote (discount shops).

Yes, that was what I was referring to. I'm going to post another question on where to find supermarkets. I've only gone to one near Tokyo Dome many years ago and if I remember correctly, it was small in size.
Thanks, AK.

2nd Q's food company "Forica Foods/ホリカフーズ" web is here.
http://www.foricafoods.co.jp/rescue/rm_boxset.html
That product name is レスキューフーズ 一食ボックス : Rescue Foods isshoku(=one meal) box.
How to cook(?) :
http://www.foricafoods.co.jp/column/column03_b.html
http://www.foricafoods.co.jp/column/column00.html
YouTuber's vids may better than official.
https://youtu.be/ROSZJDQu2Go
https://youtu.be/Cc1okqSRKjI
Wait about 30 min after heating liquid/加熱剤(kanetsu-zai) injected.

And if you like "beef" or "bowl(丼：don/donburi)" food,
you can find easier a lot of "retort pack" at regular supermarket(grocery store).
http://bloomingbloomy.up.n.seesaa.net/bloomingbloomy/image/DSC01048.JP...
http://kerokero-info.com/wp-content/uploads/2017/02/retoruto2.jpg
http://livedoor.blogimg.jp/backstreetranslator/imgs/f/0/f04ad86f.jpg
https://www.glico.com/assets/images/original/15089/
(without "rice" and heating function pack)
These are all "curry" :)
http://shin-nikki.c.blog.so-net.ne.jp/_images/blog/_e5b/shin-nikki/image/2010-11-29T00:41:36-fcb04.JPG
http://kikurageoita.jp/blog/image/%E3%83%AC%E3%83%88%E3%83%AB%E3%83%88...
Amazon sales over 400 products now.

And how about "Space food/宇宙食：Uchuu shoku"?
https://youtu.be/FSWiZlFMETo
https://youtu.be/bqsv-IKYAiI
Sales location are limited, maybe you can get "NASA" one in yr country easier.

Thank you, Maidragon.