Battery Bank w/ AC Outlet

[SpaderTanker]

My school district has decided to lend select tech students laptops to use throughout the next school year, I was one of the chosen students. The problem is the district is not giving out any information about what laptop they will be lending the students, so I don't know if the battery capacity will be enough for my 3 hour programming course and notes for the remaining 4 hours. So I've decided to play it safe and pick up a battery bank with an AC outlet, problem is they're all $100+... I'm already spending a decent amount on a backpack to protect the laptop since students have to pay for any damages (even though it's probably gonna be a $200 POS that would be cheaper to replace than to repair). If there are any ~10k mAh AC output battery banks <$60 I would love to hear it.

[007agentHP]

there arent any decent quality ones

 

a few of these

http://www.sears.com/quirky-pickup-power-4000mah-portable-battery-surge/p-00868715000P?prdNo=4&blockNo=4&blockType=G4