Hello, berries!
At the moment I’m really loving [name_u]Percy[/name_u]. I considered it as a standalone first, but it just seems a bit insubstantial. I’m not fond of [name_m]Percival[/name_m] nn [name_u]Percy[/name_u] and [name_m]Perseus[/name_m], while I love it, is just to brave for me. Any ideas? You berries always come up with something I never would have thought of!
Thank you in advance!
Peregrine + C/S name
Peregrine [name_m]Cecil[/name_m]?
I agree with @ethelmary’s suggestion
Pierce
[name_m]Pierson[/name_m]
[name_u]Jasper[/name_u]
If it helps, I know an adult [name_u]Percy[/name_u] (in his 40’s) who’s a “just [name_u]Percy[/name_u]”.
I love the idea of something like [name_u]Jasper[/name_u] [name_m]Cedric[/name_m] or [name_u]Peregrine[/name_u] [name_m]Cecil[/name_m]
Might be a stretch but…
Perrin [name_m]Cedric[/name_m]
[name_m]Rupert[/name_m] [name_m]Cecil[/name_m]
[name_m]Perez[/name_m]
Perechiah
[name_m]Pericles[/name_m]
[name_m]Casper[/name_m]
Perseo
[name_m]Pearson[/name_m]/Pierson
[name_m]Prosper[/name_m]
Actually, I have [name_u]Peregrine[/name_u] [name_m]Casper[/name_m] on my UC, but I think it’s a bit of a stretch. Thank you anyway though!
I’m slowly falling in love with Perseo!
Perry + any C name? Like [name_u]Perry[/name_u] [name_m]Caspian[/name_m] nn [name_u]Percy[/name_u]?
As an aside, I also love [name_u]Percy[/name_u] and am not fond of [name_m]Percival[/name_m] (or [name_m]Perseus[/name_m], or any other “[name_u]Percy[/name_u]” name except [name_u]Peregrine[/name_u] which is admittedly a stretch) so I know the struggle 
I searched last names for you beginning with [name_m]Perc[/name_m] and Pers, in case any of them would make a good first. I have been known to suggest Persimmon as an option for a [name_u]Percy[/name_u] nn 
I love it! Although that’s all very well for me to say when I’m not naming children any more! It is in use as a last name (and no doubt with an unrelated meaning) with these two spellings, here in the UK: Persimon and Percymon.
Here are some others (from a list of British surnames):
Perschall
Perselow/Perslow
Persham
Pershore
Persiano
Persico
Persior
[name_f]Persis[/name_f]
Percett
Percliffe
Percott
Persior and Persico are good options!
I love the suggestion of [name_u]Jasper[/name_u]! I might steal that for my own list haha!
I think [name_u]Percy[/name_u] works very all name starting with [name_m]Per[/name_m], like [name_u]Peregrine[/name_u].
Ona girl, [name_f]Persephone[/name_f]? Persepholine?
On a boy? I have no idea.
I had a friend in high-school named [name_m]Preston[/name_m] NN: [name_u]Percy[/name_u]
Preston nn [name_u]Percy[/name_u] is a good name, but unfortunately I have a bad association with [name_m]Preston[/name_m]. Otherwise I’d probably use it— thank you!
Per is a diminutive of [name_m]Peter[/name_m]— I think if someone named [name_m]Per[/name_m] something-with-a-c wanted to be called [name_u]Percy[/name_u], I wouldn’t question it. I might be surprised with [name_m]Peter[/name_m], but I’d get over the surprise pretty quickly-- it works well enough.
Also [name_u]Percy[/name_u] Bysshe [name_u]Shelley[/name_u] was just [name_u]Percy[/name_u]— you can always say “like the poet” if anyone challenges you on [name_u]Percy[/name_u] as a stand-alone name.
Other possibilities (with or without a middle name starting with a c): [name_m]Perkins[/name_m], [name_u]Perry[/name_u], [name_m]Perth[/name_m]
Also, maybe a middle name starting with the sound “see” rather than the letter? [name_u]Cooper[/name_u] [name_m]Seymour[/name_m], for example, would have [name_u]Percy[/name_u] as the middle sound.
I love the suggestion of [name_m]Perkins[/name_m] and [name_m]Pearce[/name_m] - [name_m]Pearson[/name_m]
I think you just gave me my new favorite english name for [name_m]Perez[/name_m]! 
@EllieWilbury I’m not creative enough to give any more suggestions, but I’m seconding [name_m]Perkins[/name_m], [name_u]Peregrine[/name_u], and [name_m]Prosper[/name_m]! Actually, maybe [name_u]Parker[/name_u] would work with a c middle? [name_u]Or[/name_u] an “Er” starting name - I’m blanking on them at the moment but there has to be some out there!
Edit: I’m an idiot. The name I was thinking of was Eric - maybe Phineas Eric or something along those lines?
I mean you could just go with straight [name_u]Percy[/name_u] it’s a strong enough name on its own.
I don’t think [name_u]Percy[/name_u] needs a nn myself!