From Roman Pontificals from the 13th Century (slightly adapted for modern use):
Blessing of backpack: Lord Jesus Christ, because of your infinite compassion, by the command of the Father, and through the cooperation of the Holy Spirit, you came down from heaven to seek the lost sheep, caught in the devil's snare, and to bring back heaven’s flock, carrying us on your shoulders. We humbly call upon you, most gracious Lord: sanctify (+) and bless these backpacks for those who, for the love of your name, will bear them over their own shoulders as they fulfill your command. When they petition in prayer, seek in pilgrimage, and live a worthy life, may your pilgrim servants encounter your right hand to protect them, and come safely, at last, to our true heavenly home.
Reception by bearer: In the name of our Lord Jesus Christ, receive this bag as a sign of your pilgrimage, so that having been disciplined, saved, and corrected, you may arrive worthily at the threshold of the saints. After your journey has been completed, may you return safely to your own home. By him [whose coming is certain, whose day draws near, our Lord Jesus Christ, may He live and reign forever in our hearts]…
Blessing of staff: We ask also a blessing on these walking sticks in the (+) name of the Fat her, and of the Son, and the Holy Spirit, the support of your journey, your labor and your pilgrimage.
Reception by bearer: Receive these walking sticks, which, along with the strong right arm of our Lord Jesus Christ, will sustain the steps of your journey, so that you may be able to go on safely and bravely, resisting all falls and dangers, especially the venomous impulses of the ancient serpent. When, through the intercession of the saints whose intercession you desire, your journey finishes, with God’s help and blessing, may you be worthy to return to your own country. Amen
While setting the first stamp/sello (2 Cor 1:21-22): A reading from the Second Letter of St. Paul to the Corinthians: “But the one who gives us security with you in Christ and who anointed us is God; he has also put his seal (+) upon us and given the Spirit in our hearts as a first installment.”
The Word of the Lord. Thanks be to God.
Blessing of the pilgrims themselves in their parish church: May the Almighty and Eternal God, the way, the truth, and the life, lay out your path according to his good pleasure. May he appoint the archangel Raphael, Tobiah’s companion on his journeys, as your guardian during your pilgrimage, leading you in peace to your destination and guiding you back to us safely. May the Blessed Virgin Mary, and all the saints, whose support you seek, intercede for you, that you may receive, according to your desires, prudence, peace, and forgiveness of sins, and acquire eternal life. We ask this blessing, in the name of (+) the Father, the Son and the Holy Spirit. Amen