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I have two very expensive ones that I appropriated from work so I can't recommend anything specific unless you want to pay BIGLY but I would say any small wrench that has a range of 2-40 Nm would be good. See that it comes with a set of hex bits H2-H10 and torx bits T10-T25 or T30 if possible since torx is getting increasingly more common on bike parts.
I don't think spending a lot of money is necessary because surely anything that's sold in an online bike shop is calibrated and accurate enough