Agree with avoiding the ee sound for the other one. I also feel like it should have a slight retro/vintage vibe.
Penny and:
Amber, Ariel, Alice, Blythe, Claire, Coral, Clara, Delilah, Erica, Florence, Giselle, Hazel, Iris, Judith, Juliet, Joanna, Kathryn, Leah, Lois, Lydia, Megan, Mara, Maria, Nicole, Nina, Nadia, Opal, Rosa, Rachel, Sara, Sophia, Sorrell, Tara, Tamsin, Una, Violet