Peut-tu venir avec moi pour un moment?. Ou bien,
Tu pourrais m’accompagner, si?

Technically, French inverts verbs and pronouns to ask questions, or uses a question tag, such as “est-ce que”. Therefore, the way to ask your question would actually be “peux-tu venir avec moi pour une seconde?” or “est-ce que tu peux venir avec moi pour une seconde?”.

If you want to be more formal, you would use “vous” instead of “tu” and conjugate the verb accordingly (pouvez).

However, if you are being more familiar, you can forgo the verb-pronoun inversion and indeed say “tu peux venir avec moi?”. In that case, the question will usually be understood by the time of voice used.

First, the pour preposition is unexpected here and can be omitted. Yes, it must be said that sometimes it can be a valid preposition to introduce a period of time, but it’s less and less used and would sound very formal¹, like out of a book or an old song. The reverse interrogative form (peux-tu / pouvez-vous) would be odd for the same reasons, which leaves the forms est-ce que … or even preferably the affirmative phrasing with interrogative intonation (most common).

On another matter, incidentally, the default short time in french (not mathematically but linguistically equivalent to the english a sec) is quite often deux minutes, so you could use any of these idiomatic ways of saying it :

Tu peux venir avec moi deux minutes ?

Tu peux venir voir (quelque chose) deux minutes ?

Tu peux venir me voir deux minutes ?

¹ I assumed from your question’s phrasing that you were adressing a friend or close relative, not the Ministry of Foreign Affairs or something…