There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
-(n)dil
suffix. -friend
-dil
suffix. -friend
-nil
suffix. -friend
nilmo
noun. friend
-dildo
suffix. -friend
-el
suffix. friend
-iel
suffix. -friend
-nildo
suffix. -friend
-ser
suffix. friend
elendil
masculine name. Elf-friend
elesser
masculine name. Elf-friend
helde
noun. friend
heldo
noun. friend
helmo
noun. friend
málo
noun. friend
sermo
noun. friend
seron
noun. friend
sondo
noun. friend
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A variant of Elendil appearing in The Etymologies from the 1930s (Ety/SER), perhaps a compound of the root ᴹ√ELED “star-folk, Elf” and the suffix -ser “friend”, as indicated by the archaic form †Eleðser.