No, the second attack is not at advantage, you are no longer hidden

The rule from the the PHB p. 195 about attacking from hiding is:

Unseen Attackers and Targets

When a creature can’t see you, you have advantage on attack rolls against it.

If you are hidden—both unseen and unheard—when you make an attack, you give away your location when the attack hits or misses.

If a character is hidden and as its action it attacks, the first attack out of the ones available to it (Extra Attack, the bracers you mention, etc.) is at advantage due to the rule above: "When a creature can’t see you, you have advantage on attack rolls against it".

However the second part of the rule, "you give away your location when o attack hits or misses" refers to a solteiro attack, "o attack", not to the entire Attack action (or the action used with the bracers to attack). This means you have given your position away and any further attacks as part of the same action are not at advantage unless there is another reason for it.

This answer has so far described how the Attack action works with the "attacker is hidden" rules, which is not technically the action described in the bracers item. However this exposes a flaw in the description of the item which introduces significant ambiguity: there is no actual rule for the item specified that allows a RAW ruling about how it exactly works with the hidden rules. As such the only way to answer this question, without diving into potentially complex and un-balancing rules, is to assume that the action used by the bracers to attack works in the same way as the Attack action does. Of course this is now in the realm of DM fiat.

I do not think you stay hidden after the first attack. Otherwise the Skulker Feat is almost useless, as it states:

When you are hidden from a creature and miss it with a ranged weapon attack, making the attack doesn't reveal your position.

That feat overrides this general rule

Unseen Attackers and Targets
When a creature can’t see you, you have advantage on attack rolls against it.

If you are hidden—both unseen and unheard—when you make an attack, you give away your location when the attack hits or misses. (PHB. p. 195)

You would get advantage on both of the attacks

Let's have a look at the wording in the PHB:

PHB Page 192:

Attack

The most common action to take in combat is the Attack action,...Certain features, such as the Extra Attack feature of the fighter, allow you to make more than one attack with this action.

PHB Page 195:

Unseen attackers and targets

When a creature can’t see you, you have advantage on attack rolls against it.

If you are hidden—both unseen and unheard—when you make an attack, you give away your location when the attack hits or misses.

Let's differentiate the 'Attack Action' and an attack. A single 'Attack Action' can be compose of multiple attacks, as in the extra attack feature.

Now look at the second part of the 'Unseen Attackers' wording, I think it is implied that it should read:

If you are hidden—both unseen and unheard—when you make an attack action, you give away your location when the attack hits or misses.

Now this is obviously up to interpretation so I'd love to see what other people think too.