Hello Opad.
You can use MTN internet sim cards (which is what I am using now to type this message from my laptop) The Internet sim card cost N13,690 you would need a Phone that is GPRS enabled (I am using motorola L6) and connecting via the blue tooth function alternatively instead of using a phone, you can use the MTN GPRS modem which is about N24,000 - N28,000. With the MTN sim card you can browse 24hrs. You get to pay N13,500 monthly

Alternatively you can use GLO direct, I am not so sure of their rates but I think you get the Internet sim for N12,000 and their GPRS modemfor N25,000. It only works with laptops unlike MTN which you can use for desktop. Glo helps you configure and installs while with MTN you would do it on your own. You pay a N12,00/month fee for 24hrs.

With any of them, you get to browse any where you have a Glo or MTN conncetion. I hope that was helpful