I think "I bring a blanket" should also be accepted. When I lived in Italy with a host family, the parents would often say to their kids "Prenda una mela." In English, this would become, bring me an apple, not take me an apple. Therefore in this context I think both translations can work.
A duvet and a comforter are two different things, except in rare cases in the UK where what is called a comforter in NA is also called a duvet. In my experiences on the island and both continents it is 'comforter' which is the least known, as in the UK and EU they only use 'duvet' and in NA people are still likely to know what a duvet is.
Regardless, I assumed given the context of 'la coperta' that it would be referring to the item covering one's bed, over the bedsheets (or 'linens' as they say in the UK, which is also a problem and a word I suspect is more etymologically related to 'le lenzuola' than 'bedsheets'). If so, 'blanket' is the least likely translation of this word unless it also refers to the item which is commonly folded at the end of the bed in winter or which tends to grace one's sofa. Either way, if it does refer to the former, 'duvet', 'comforter', 'coverlet', 'bedcover' are all words that should be accepted.
I agree with you both (Gianluca & Wiijimmy). True it's technically the present tense, but Italian as English will often use/often uses the present tense with future meaning. What it boils down to is context and in this example, that's missing, so in its absence you'd have to go with the present tense.