A couple of years prior to my retirement, we were replacing two "trash rack cleaning machines" at two of our remote hydroelectric plants. The original trash rack cleaning machines rode on inverted angle iron rail, and it was a source of continual problems. After about 20 years, with other problems with the trash rack cleaning machines, we were going to replace them. I had been asked to make recommendations for some replacement rails and how to mount and join the rails. I called for a rolled steel rail with "Thermit" welded joints. We left the sizing of the rail up to the manufacturer of the new trash rack cleaning machines. We got what looked like a light railroad rail section, but was in actuality, an ASCE crane rail section. I am guessing it was all of about 2" across the top of the railhead, and probably about 5" wide on the bottom flange. The vendor for the trash rack cleaning machine and the installation contractor had no problem in getting the new rail, and in getting Thermit molds for the welded rail joints.
After I retired, the old bridge cranes in each of those two plants were replaced. Sad day, as those were classic old cranes with the riveted "fishbelly" crane girders and open gearing on the hoist trolleys. Those cranes had two trolleys apiece, each with a 20 ton capacity hoist. Smaller bridge cranes were in each plant's headgate room to handle stoplogs. In the course of the replacement, even the crane rails were removed and scrapped. Not sure the section or weight of it.
The old crane rail had a few divots in it where the end truck wheels had slipped and spun. There was plenty of rail that went to the scrapper. Relating this gets me to thinking. In your search for crane runway rail, perhaps the thing to do is to contact shops which install, repair, or upgrade bridge cranes. Ask if they are doing any jobs where the crane rails are being replaced, and inquire about buying the used rails. Getting the rail is only part of it, as you will need the joint bars and bolts for them, along with clamps or "J" hooks to hold the rail and align it on top of your runway beams. The problem with jobs where the rails are going to be replaced is that the rails may well be cut into convenient lengths with a gas axe, with the priority being handling the rails as scrap rather then for re-use.