Regarding the Cloak, one possibility is that Harry could duplicate it using the Time Turner. (Harry[1] goes back in time, equips himself with Cloak[1], sneaks up to Harry[2] and take Cloak[2] from his pouch. He could use both cloaks to perform an impossible rescue, then return Cloak[2] to Harry[2]’s pouch.)
Regarding the Cloak, one possibility is that Harry could duplicate it using the Time Turner. (Harry[1] goes back in time, equips himself with Cloak[1], sneaks up to Harry[2] and take Cloak[2] from his pouch. He could use both cloaks to perform an impossible rescue, then return Cloak[2] to Harry[2]’s pouch.)