I believe one can still obtain this stock via B&H in the U.S. as a non-returnable special order item. It comes in, I think, non-perforated rolls of 400 feet and 200 feet at 9.5" width. It's called
Aerochrome III Infrared Film 1443, and from the looks of it, its composition is very similar to EIR, if not the exact same stuff (like EIR, it's on an estar base with one emulsion layer sensitized to infrared wavelengths). Apparently, there is/was another stock called SO-734, which does not appear on the B&H web site and may no longer be produced. SO-734 apparently has/had greater sensitivity to IR wavelengths (possibly longer wavelengths one might expect from HIE, which is sensitive to at least 900nm).
Of course, such stock is of little utility to 35mm, medium or large format applications without another party arranging to cut down one of these rolls to size. I'd totally be for finding someone willing to cut a spool (down to 120, 4x5 or 8x10, knowing that perforation for 135 might be another step atop merely cutting it down) and buying from them.