I'm not sure if they release those to dvd or not, and you'd likely not be able to find them with English subs or in our region for that matter (easy to work around though).
You could try http://www.hmv.co.jp/?lang=en
Both Japanese sites -more for movies and music, shipping is pricey but quick if the item is in stock..
which as you can see, sells more than just Japanese stuff.http://www.amazon.co.jp/
would be more difficult, but is possible and more likely to have tv shows.
I've ordered from the first three in the past without problems.
Another option is looking for fansub groups... Admittedly when I wanted a clip from some Japanese show, I've always downloaded them from Japanese open nap servers.