So after I identified GCC 2.6.3 for a matching decompilation project (Built/Distributed Spring 1995 according to SCEA BBS) was the right compiler version, it was quite annoying to learn that this version of the compiler seems to not be available anywhere online. In fact, it's the only compiler version that I found to exist that wasn't available online. After discussing from Xeeynamo from the Castlevania decomp project, it seems they might also need this compiler.
So why is this compiler hard to find?
It seems that this compiler was short-lived, and may have only been distributed on a standalone floppy disk.
PsyQ's GCC 2.7.2 build was built in December 1995, less than a year after PsyQ's GCC 2.6.3 was built. And unfortunately, SN Systems seemed to only start distributing the compiler on the Programmer Tool CDs starting with GCC 2.7.2. So, this compiler was very short-lived and it was only distributed on floppy disks. And many of these floppy disks don't even include PlayStation / SN Systems branding on them, so it's hard to even realize they are tools for the PlayStation.

So what exactly am I looking for?
I'm not a collector, I don't need the physical floppy disks, just the files on them. This in turn will help give modding and decomp communities (such as Castlevania & Frogger) a way to do our job better.
It seems the floppies containing the files I'm looking for came with the DTL-S2110 adapters.
The version (v4.00, v4.02, v4.04, etc) do not necessarily indicate the compiler version on your floppy disks.
The thing to determine is the
This image shows all of the images of these floppies I was able to find, and which ones are important / not.

So, does anyone have these? Let's chat about it

There's some additional nuance to this, which I thought I'd explain for those who want it, but it's probably not necessary for the main part of this post.
Because GCC 2.6.3 is an open source project following the GPL license, all modifications to GCC are required to have their source code available, if at least for a limited period of time. Likely because of the limited storage space on floppies, SN Systems didn't include the source code of their GCC fork with the binary until we reached GCC 2.7.2 and GCC 2.8.1, which were distributed on the Programmer Tool CDs.
But, because GCC 2.7.2 was included, this was enough for myself & others in the decomp community to attempt to apply the changes seen in the GCC 2.7.2 version to a clean version of GCC 2.6.3. This worked surprisingly well, and both a Win32 and Linux x64 build were made. However, not all of the changes are clear, and there's some behavior that seems like it may not be exactly the same as the original. So, having the original version (even if it's DOS / 16-bit) gives us the final piece needed to make our builds usable on modern systems match the original perfectly, since we can compare against it.