Because you need to hold it in your hand which would invalidate most magus subclasses as they either need a free hand or hold a 2-handed weapon!
Sparkling Targe seems the obvious answer to me, given that you have a natural weapon available. Starlit Span also works when using 1-handed range weapons.
That said, you can’t generally use items for Spellstrikes, though there is a feat that lets you use scrolls.
The problem is that you don’t cast directly, you activate the item, and that activation casts the spell for you.
The flow is spellstrike->cast->attack
An item is Active->cast(from item)
Spellstrike doesn’t have the opportunity to activate an item, as that is a separate Action.
Mind, if I was your GM, I would allow it with a Tengu Feather Fan, as other races have innate spells, but not with other items. But you will need to talk with your GM about that.
You can use items to Spellstrike as long as their activation action is “Cast a Spell”. Feats like Striker’s Scroll and Fused Staff primarily avoid you needing the Scroll/Staff in hand.
The issue here is that the Tengu Feather Fan’s activation action is “Interact”.
