For me the most natural is:
I need the laptop for work.
'too work' is wrong. I think you mean 'to work' which is grammatical, but means that you need the lap top itself to function (i.e. to not be broken).
'I need the laptop for my job' is fine, grammatically. 'I need the laptop in my job' is also grammatically fine. Both of these could easily be said and native speakers wouldn't bat an eyelid, but for me 'work' sounds more natural.