I don't know if TRE used a proprietary or custom EGT probe (also known as a thermocouple) but I'm going to go out on a limb here and say that I highly doubt it. I'm pretty sure it was stated before that TRE simply stocked K-Type
"exposed junction" probes, which simply means that the 'wires' (for want of a better description) that measure the heat (or more accurately reference it) are exposed and not protected by any sheath. This leads to a very fast response time and is why many users report being able to see temperature variations whilst changing gear and simply revving on their driveway. As is always the case, you don't get something for nothing and the downside of the faster response time is a shorter service life. These type of probes do not withstand pressure or any type of corrosion well so you may find that probe placement or the type of fuel used (plus your tune) could affect service life. That said, plenty of people seem to see 15-20K service lives, which might not be as good as the life span of a good quality O2 sensor but it's not that bad either.
If you really want the TRE probe, maybe try sending Harry (number3) a nice PM. He is good friends with Jon and seems to be able to get a hold of him when others can't. I'm sure he can find out if TRE still sells these and even if they don't, I can't see why Jon wouldn't want to disclose which manufacturer they used. Post up if you find out, it would be good information for the board to know even if today the EGT is a less widely used tuning tool than the AFR Gauge. I'd almost put money on it being a big brand name like Bosch.
If you have no joy with the TRE probe then start shopping around on the net for exposed junction K-type EGT probes.
Paul.
Edit: No, not all thermocouples are universal in application or intended for automotive use. The designation "K-Type" indicates that the thermocouple has a specific temperature range in which it can be used. These links have some basic but quite useful information.
Introduction to Thermocouples
How Thermocouples Work