Asus K50AB and external battery

Hi everyone,
First I'd like to say that I am a very big noob when it comes to electronics, I can easily perform a craniotomy but I have no idea what a Watt stands for.
Well, I bought an Asus K50AB some time ago and the battery life is about 2 hours but I need more, So I was thinking of buying an external battery but I don't know which of them will work with my computer.
My laptop's power specifications are the following:
Battery Pack & Life 6 cells: 2200 mAh
AC Adapter Output: 19 V DC, 3.42 A, 90W
Input: 100-240 V AC, 50/60 Hz universal
This is what the Asus official website says but instead of 3.42A the panel on my AC adapter says 4.74A.

There isn't a big choice of batteries in my country but I will give you the specs for the ones that I could find:

Prestigio Power Bank 501
Battery Technology Lithium Ion Polymer
Voltage Provided DC 5, 6, 7.5, 9, 12, 14, 16, 19 V
Maximum Output Current 3.5 A
Output Power 45~50 W
Battery Current Capacity 10000 mAh
Battery Recharge Time 4 hr
Output Power Connectors Type USB, Notebook Power Connector

Triax EL95
Capacity: 95Wh (6900mAh)
Voltage: 5V, 12V, 16V, 19V
Output: 5V/0.8A
12V/1.5A
16V/4.5A
19V/3.5A

Triax El65B
Capacity: 65Wh (4600mAh)
Battery Technology: Li-Ion
Voltage: 5V, 12V, 16V, 19V
Output:5V/0.8A
12V/1.5A
16V/4.5A
19V/3.5A

Triax El135p
Capacity: 135Wh (8600mAh)
Battery Technology: Li-Po
Voltage: 5V, 9V, 12V, 16V, 19V, 21V
Output:5V/0.8A
9V/1.2A
12V/1.5A
16V/4.5A
19V/3.5A
21V/3.5A

I am a bit confused because none of this batteries seem to have the same number of Watts or Amps as my laptops AC adapter.
Please tell me which of these batteries can I use for my laptop...
Please help, you are my only hope...