Difficult to help without some examples of what you and he like.
Well used but not massively popular, right now at least:
Amy, Alexandra, Amber, April, Bronte, Bryony, Bethan, Bianca, Claire, Carys, Clarissa, Camilla, Daphne, Daniella, Dana, Dorothy, Esther, Elise, Emma, Evangeline, Felicity, Francesca, Fiona, Faith, Georgina, Gabriella, Genevieve, Greta, Hannah, Hermione, Hallie, Hope, India, Ida, Iona, Iris, Juliet, Joanna, Jade, Jocelyn, Kirsten, Kayla, Kendra, Keziah, Lara, Lois, Leonie, Lauren, Miranda, Maeve, Melody, Martha, Niamh, Natasha, Naomi, Natalie, Ophelia, Octavia, Opal, Olive, Philippa, Pearl, Paris, Paloma, Robyn, Romilly, Rebecca, Rhiannon, Sadie, Saffron, Susannah, Saskia, Tamara, Tamsin, Thea, Tegan, Victoria, Verity, Vanessa, Viola, Zoe
Adam, Alban, Anton, Aston, Benedict, Bruno, Christian, Cory, Cosmo, Callum, Declan, Damien, David, Dominic, Elliot, Ellis, Ewan, Edmund, Fergus, Ferdi, Frank, Gareth, Gregory, Hal, Hugo, Hugh, Ivan, Jude, Jesse, Jasper, Jeremy, Kieran, Kit, Liam, Luke, Matthew, Micah, Mark, Morgan, Nicholas, Nathaniel, Owen, Orson, Otis, Patrick, Peter, Percy, Phillip, Rhys, Robin, Robert, Rowan, Solomon, Seth, Simon, Stanley, Timothy, Victor, Vincent