And I don't think by the way that a party of "righteous" Jews exist nowadays. The Qur'an does not say so either, it says:
Indeed, those who believed and those who were Jews or Christians or Sabeans [before Prophet Muhammad] - those [among them] who believed in Allah and the Last Day and did righteousness - will have their reward with their Lord, and no fear will there be concerning them, nor will they grieve. [2:62]
A righteous Jew has to be a Muslim because the religion in the sight of Allah is Islam, and that's known by everyone. A Jew cannot be "righteous" if he's not a Muslim, his good deeds will not save him from the punishment of Allah, his example is like a Buddhist, Hindu, etc who also does good deeds but with no faith in Allah.
Another important point, someone's beliefs can reflect someone's manners, and someone's manners can reflect someone's beliefs. The Qur'an gives you ideas about that in Surat-Al-Ma'oon:
Seest thou one who denies the Judgment (to come)?
Then such is the (man) who repulses the orphan (with harshness),
And encourages not the feeding of the indigent.
[107:1-3]
So a righteous jew seeing Islam instructing righteousness has no any pretext to stay away out of it, Islam is the way of every human's life, after the descendant of the Qur'an, none is excused and everyone is warned.