PGP - The elusive source!
In my continued travels through the murkier depths of ARCHIVE.ORG, I have found this, the historic root of all things PGP - as far as such a thing exists.
You should be able to browse this (using the timeline, in particular) to find and restore old freeware and commercial versions of PGP. Perhaps even regain the ability to unlock those old encrypted disks and files you created long ago (assuming you still have those keys) 
Here's a "worked example" (since using it to gain actual access to executables is not quite straight forward - as I demonstrate below).
First off - get to the root of (what might be) the oldest archived HTML website for PGP:
https://web.archive.org/web/19981206035637/pgpi.org:80/
We shall go directly to attempting to locate the "earliest" versions of PGP that we can find by this approach.
Remember that we can also use the Wayback Timeline at any stage to alter our chances of having slightly different links to slightly different offerings. But we'll keep it simple for now... After all, a selection of 49 varieties of freeware sounds quite tasty...
Oo - just look at all those supported operating systems! Let's try one - say, a freeware version for MS-DOS?
Hmm. PGP 5.0i was clearly current in 1999, so if PGP 2.6.3i is still being offered on the very same page, it must a bit older than 1999 and thus more likely to work on even older versions of DOS...
Language files? Hm, make a note of that. Also it means that the primary package is probably in English so let's see if we can get that first...
Er, ok - so this is clearly not going to work quite as hoped. Archive.org's Wayback Engine does not process FTP sites. This is hardly surprising, as to do so would require all the hard drives of this planet, the moon, and probably Mars. (Hmm, servers on Mars? They'd be running nice and cool).
Told ya! But fear not, because here comes the "special sauce". Watch.
We shall take just some of the trailing part of that FTP path. This will provide some context so that we are more likely to find FTP sites that contain "sunset"-type archives of our file...
And sure enough...
Amongst all of those potential sources (and probably a few dead or dodgy links) a couple stand out. Debian sounds good - and being a mirror of ftp.sunet.se sounds encouraging...
PAY-DIRT!
ftp://ftp.fi.debian.org/mirror/archive/ftp.sunet.se/pub/security/tools/crypt/pgp/pgpi/2.x/pc/msdos/pgp263i.zip
And that, my friends, is how it is done.