How about a stylish slim wallet and a matching accompanying (or at least not contrasting) smartphone pouch?
A pouch is basically the style where you take out the phone for use:

As there are nowadays as many sizes as many phones if you don't have a more 'standard' sized phone (think iPhone) you really have a hard time to find a good one for your phone.
And we haven't talked about your smartphone pouch to match your wallet.