No.1 - I have tried to find Half-Life Alpha Builds myself several months ago by attempting to ask People who were credited on the game. (Mainly Former Valve or Sierra Employees) Most have yet to respond, And the few who did respond told me they did not possess any build of the Game.
No.2 - Most Magazines I have viewed from 1998 (Mainly via this Website) -
https://www.hl-inside.me/magazines/ appeared to share the same Photos between each other (e.g. Mainly the ones from 97 etc.) and even if they did have a Build, Those appeared similar to the Net Test Builds that were uploaded a few weeks ago with some minor differences.
No.2A - In regards to the E3 Build itself, The Only Magazine I'm aware of that did have access to it was Gamer's Republic. -
https://www.hl-inside.me/magazines/gamers-republic/GI_1998-09_4/ But even the staff that I contacted have told me that while they did have access to the Build, Neither of them owned it.
A few months ago, I did start a Group dedicated to Getting Valve Interested in seeing the Support to considering either letting more Half-Life Alpha/Beta Builds become Public or at least Release Stuff (Such as Model and Map Sources) not in the SDK. -
https://steamcommunity.com/groups/get_half-life_alpha_released However I now consider it to be slightly out of Date and I may Revamp it at some point along with adding a Announcement about the Net Test Builds getting Uploaded.
But to Answer in Short: While it does sound like a Good Idea to ask People about if they have a Half-Life Build they could upload, It's not quite simple. However, Tyler McVicker posted back in September after Net Test 2 was uploaded saying that six People came forward who told him they did have Beta Builds of Half-Life, So All I can say is to simply wait and see what happens.