How exactly does one install shower glass if there is no stud in the wall at the point of mounting?

I want to install a frameless shower glass enclosure (3/8"/10mm glass, about 75 pounds) . The closest stud is a few inches away, so not really helpful. The wall layers are: tile (to be installed soon) then new drywall (mold resistant) then insulation board then brick.

I would like to avoid tearing the wall to install new studs. I should also mention this is a 100 year old house that we recently renovated. So while the drywall is new, it is over lath and plaster.

Will heavy duty toggle type anchors work? I found a video online where the poster used toggle anchors and says the glass door's been stable for 6 months. I'm not very convinced this would hold steady for the long term. If the recommendation is for this, are there specialized toggle anchors meant for tile?

I'm hoping there are specialized heavy duty glass clamps/brackets that are designed for such "studless" situations. Even better if there exists a glass clamp with long bolts that can anchor into the brick layer behind the drywall.

One small but maybe important detail - the small section where the glass would anchor to the wall does not have lath & plaster. It was accidentally removed during the renovation which we later filled with insulation (section measures about 4-6 inches wide, floor to ceiling). So strictly speaking, the glass clamps would see the following layers: tile then drywall then insulation board then brick. If it matters, the rest of this bathroom wall has the following layers - tile then drywall then lath & plaster then brick.