I only recently became aware of this work and have managed to find a used copy from Germany:
Die überzeitliche Einmaligkeit des Heils im “Heute”: Zur theologie des Hebräerbriefes. Neuried: Ars Una, 2002.
Blurb translated from the back cover:
author examines the meaning of the words 'hapax' and 'ephapax' in Hebrews, which are usually translated as 'once for all' and
understands them on the basis of their origin and context in the sense
of 'once finally' and 'at once finally', which is of considerable importance for sacramental theology. It
has been shown that, according to the Platonic-Philonic model, the symbolism of the last 'day' in the pointedly
used 'today' presupposes a Greek understanding of time, which was
abolished by the God-human act of salvation in the eternal today of God. Thus,
the final uniqueness of the 'perfection' effected by
Christ is clarified, which is accomplished in 'sanctification' by
means of baptism, Eucharist, and other ways, by direct and common
the sacrifice which has happened historically and at the same time
exists in his person."