Ways to make a natural weapon magical that don't require attunement?

[ATHATH]

Is there, say, a ring or an amulet or a spell or something that I could give to one of my summons from one of the UA summon spells (which only last for up to an hour, hence the "no attunement" clause) to make its natural weapon attacks (specifically, the claw attack of the putrid summon from the Summon Undead Spirit spell) pierce resistance to nonmagical damage?

[Chronos]

If a natural weapon counts as "a weapon", then you could cast Magic Weapon or Elemental Weapon on it.

Previous editions had a separate spell, Magic Fang, just for natural weapons. I'm not sure if it was the intent that it be rolled into Magic Weapon now.

[JackPhoenix]

6 levels of Shepherd druid, assuming you stick to fey and beasts.

Insignia of Claws doesn't require attunement.

[da newt]

You may be able to homebrew craft an item that gives the effect of a spell - (pg 128 XGTE / DMG pg 284).

[Yuroch Kern]

Technically, you could use Alter Self, a 2nd level Transmutation, to give it a +1 natural attack, assuming you make a scroll or something it can use first.

[ATHATH]

Technically, you could use Alter Self, a 2nd level Transmutation, to give it a +1 natural attack, assuming you make a scroll or something it can use first.
I don't think that that would work.

Natural Weapons. You grow claws, fangs, spines, horns, or a different natural weapon of your choice. Your unarmed strikes deal 1d6 bludgeoning, piercing, or slashing damage, as appropriate to the natural weapon you chose, and you are proficient with your unarmed strikes. Finally, the natural weapon is magic and you have a +1 bonus to the attack and damage rolls you make using it.
It looks like just the natural weapon created by the spell is magical. Is there a Sage Advice ruling that contradicts this or something?

[Yuroch Kern]

I don't think that that would work.

It looks like just the natural weapon created by the spell is magical. Is there a Sage Advice ruling that contradicts this or something?

Didn't find a ruling, although the claw attack in question does not seem to necessarily use both hands. The multiattack blurb just says more attacks for the spell level. I don't know what your table's rules on potion creation are, because an Oil of Alter Self is useful even beyond augmenting summoned creatures.

[Greywander]

The Insignia of Claws, from Hoard of the Dragon Queen. It's an uncommon magic item with no attunement that gives +1 to attack and damage rolls with unarmed strikes and natural weapons, and makes them count as magical.

There's very few magic items that influence unarmed strikes. This might be the only one, actually. It's not amazing, it might be nice to see +2 and +3 variants, along with others that compare to magic weapons such as Flame Tongue or Holy Avenger. Poor monks. But it is only uncommon and doesn't require attunement, so it shouldn't be too difficult to get one as long as your DM is willing to cooperate.