how to get SIM with Internet access?

This Wednesday I will arrive at Tokyo and stay in Japan for 3 weeks.

I'm looking for a sim card with Internet access for my mobile phone. 1gb limit is more than enough for me. I was looking at
http://www.bmobile.ne.jp/english/product.html
but I'm already too late ordering it . They list need that they need 7 days processing time.

Is there something similar to get somewhere in Tokyo or preferably the Narita airport?

or is there a better option? I must stay below 10k yen for the entire period.

http://www.bmobile.ne.jp/l_1gb/index_en.html

this is local version of prepaid data sim card for bmobile..

it's 1GB for 30 days, roughly 3,500yen and you'll need a local/japanese phone no. in order to activate the sim.

if not, you'll pay extra 2,500yen for "activation service", note that this is credit card payment only.

it's all mentioned at the above links, where to buy at Tokyo or website(ship next day)

Contact B-mobile and have them ship it to your hotel. It may arrive a few days late, but you'll have it for the bulk of your trip.

Or check out global advance, as they can fulfill in 2 days and they are still around your budget. You should also consider a pocket wifi too for ease of setup.

http://www.globaladvancedcomm.com/