It seems to me that the blessing is not required, rather the bishop’s permission, as I highlight in
bold below.
From the 2004 Instruction Redemptionis Sacramentum:
[155.] In addition to the ordinary ministers there is the formally instituted acolyte, who by virtue of his institution is an extraordinary minister of Holy Communion even outside the celebration of Mass. If, moreover, reasons of real necessity prompt it, another lay member of Christ’s faithful may also be delegated by the diocesan Bishop, in accordance with the norm of law,[256 footnote: Cf. Code of Canon Law, can. 230 § 3.] for one occasion or for a specified time, and an appropriate formula of blessing may be used for the occasion.
This act of appointment, however, does not necessarily take a liturgical form, nor, if it does take a liturgical form, should it resemble sacred Ordination in any way. Finally, in special cases of an unforeseen nature, permission can be given for a single occasion by the Priest who presides at the celebration of the Eucharist.[257 footnote: Cf. S. Congregation for the Discipline of the Sacraments, Instruction, Immensae caritatis, prooemium: AAS 65 (1973) p. 264; Pope Paul VI, Apostolic Letter (Motu Proprio), Ministeria quaedam, 15 August 1972: AAS 64 (1972) p. 532; Missale Romanum, Appendix III: Ritus ad deputandum ministrum sacrae Communionis ad actum distribuendae, p. 1253; Congregation for the Clergy et al., Instruction, Ecclesiae de mysterio, Practical Provisions, art. 8 § 1: AAS 89 (1997) p. 871.]
The last footnote is at
vatican.va/roman_curia/pontifical_councils/laity/documents/rc_con_interdic_doc_15081997_en.html :
"§ 1. The canonical discipline concerning extraordinary ministers of Holy Communion must be correctly applied so as to avoid generating confusion. The same discipline establishes that the ordinary minister of Holy Communion is the Bishop, the Priest and the the Deacon.(96) Extraordinary ministers of Holy Communion are those instituted as acolytes and the faithful so deputed in accordance with Canon 230, § 3.(97)
A non-ordained member of the faithful, in cases of true necessity, may be deputed by the diocesan bishop, using the appropriate form of blessing for these situation, to act as an extraordinary minister to distribute Holy Communion outside of liturgical celebrations ad actum vel ad tempus or for a more stable period. In exceptional cases or in un foreseen circumstances, the priest presiding at the liturgy may authorize such ad actum.(98)
It difficult to understand “to distribute Holy Communion outside of liturgical celebrations”. If Holy Communion is being distributed, then it is a liturgical celebration. It is a ceremony that is in the liturgical books: Roman Missal or Holy Communion and the Worship of the Eucharist Outside of Mass.