I think Hal Porter is supercool!
Also don't see the problem with Henry Porter. It doesn't sound that much like Harry Potter in my accent.
That said, I definitely wouldn't use Harry as a nn, which maybe isn't what you want to hear. All the boys with Harry as a nn where I live seem to have Harris or Harrison as a long name anyway. I think a lot of people have forgotten that Harry is a nn for Henry and think of Harry and Henry as different names.