Apple as we know it is very strict when it comes with storage capacity of the device, the company keeps their devices get untouched with other brands except their own making, from battery, IC, and Processors. But there is a rumor that SanDisk have developed a hard case for iPhone that has a built-in storage that can reach up to 128GB and that's not only the good news folks, the said case happens to have an extra slot for battery with 1900mAh but this optional slot can cost about $40.
But since apple has many versions of iPhone to choose from, sadly this iXpand case is only compatible with iPhone 6 and iPhone 6S, and is available with 32GB, 64GB, and 128GB of extra storage for $59, $99, and $129, respectively. there are also 4 colors to choose from, you can choose Red, Grey, Sky and Mint and it is available now on
Amazon