Abernathy
[name_u]Ainsley[/name_u]/[name_u]Ainsly[/name_u]
[name_u]Albany[/name_u]
[name_m]Anthony[/name_m]
[name_u]Ashby[/name_u]
[name_u]Ashley[/name_u]
[name_u]Aubry[/name_u]
[name_m]Eddy[/name_m] (nickname-name but stand well on its own)
[name_u]Embry[/name_u]
[name_m]Esley[/name_m]
And then not quite and E-y combo but [name_m]Emrys[/name_m] might appeal to you.
Names similar to Alder in sound:
[name_m]Alastair[/name_m]/[name_m]Alaster[/name_m]
[name_m]Abner[/name_m]
[name_u]Alden[/name_u]
[name_m]Aldous[/name_m]
[name_m]Archer[/name_m]
[name_m]Asher[/name_m]
[name_m]Aldwin[/name_m]
Similar thematically to Alder:
[name_u]Ash[/name_u]
[name_u]Aspen[/name_u]
[name_m]Birch[/name_m]
[name_u]Elm[/name_u]
[name_u]Cedar[/name_u]
[name_m]Forrest[/name_m]
[name_m]Hawthorn[/name_m]/[name_m]Hawthorne[/name_m]
[name_u]Linden[/name_u]
[name_u]Oak[/name_u]/[name_u]Oakley[/name_u]
[name_u]Rowan[/name_u]
[name_m]Sylvan[/name_m]