Not sure if anything like this exists already. Basically a once off use of Titan Shield that cannot be moved. Something for characters who don't wear powered armour.
Shield Grenade (Usage 1)
When thrown the grenade generates a wide, unidirectional energy shield that protects against incoming attacks. The shield extends along three continuous edges in a straight line with the grenade at the center. The shield provides cover against attacks coming from the far side of the shield but not against attacks originating from the side you're on. The shield cannot be moved once activated and is depleted once used.
Was thinking 1 minute duration before the power source fries. Not sure on item level or cost etc.
It should target a grid intersection to match other grenades. I would suggest only two edges of cover.
A 1 min duration is probably fine, but if you want it to be cheap and affordable, deployable cover is maybe a little too good. I would suggest something like 'is destroyed after a number of attacks have missed you equal to 1/2 item level, minimum 1'.
Higher level versions should maybe do different things. A low level shield shouldn't block movement, a high level shield should, etc.
Clearly, it's too strong that way. As soon as your players will reach the level of the grenade, they'll be able to buy a bunch of them and be easily immune to range attacks.
I like Garretmander idea of having different version with different levels, to avoid your players to stack a bunch of them. I would state that a Shield Grenade only blocks attacks coming from a weapon/creature of a level/CR equal or lower to the level of the grenade.