Dear Nikos & Samuel,
Christ is Risen!
Appended are the katavasies for the Feast of the Elevation of the Holy Cross in English (by Fr. Serapheim Dedes).
Other than these, there is little else of significant density for a chantor at the Baptism sacrament.
From the
www.goarch.org site:
http://www.goarch.org/chapel/liturgical_texts/catechumen
and
http://www.goarch.org/chapel/liturgical_texts/baptism
Traditionally, during the baptism service proper, the first phrase of Psalm 31:
"Blessed are they whose iniquities are forgiven, and whose sins are covered." is chanted. From, here:
http://analogion.com/forum/attachment.php?attachmentid=28404&d=1275124720
You can possibly adapt the music to the English phrase.
Also, although the priest usually chants the Mode Plagal 4th Troparion:
"A robe of divine light bestow upon me, O You that for vesture array Yourself with Light; and bestow many mercies, O Christ our God, who are plenteous in mercy.", if the chantor will do it, again, look at the Greek version and use that melody as a basis:
(again, from here)-
http://analogion.com/forum/attachment.php?attachmentid=28404&d=1275124720
And, there is Fr. Ephraim, and Fr. Dedes' versions of "As many of you as have been baptized into Christ, have put on Christ. Alleluia.(3)" that one can use.
Hope this helps you.
NG