Have you tired Techpowerup they have quite the selection of GPU BIOS's and they go back quite aways.

Unfortunately, these go back to the GeForce 6xxx series, just 1 generation above of what I need. In the meantime I've found a collection of whitebunny BIOSes which contained one (noname GeForce 5500) useful for me. I wish someone backed up the mvktech.net collection. Or at least a contact to Mavke, maybe he has a backup.

Heh that was me, I made a tidy version of the Internet Archive's record of the BIOS files from Whitebunny's site. That one wasn't so bad because it was a pretty simple site that didn't use a CMS or FTP. Sadly mvktech's site essentially blocked Internet Archive from downloading anything so from what I can tell there's no actual files stored on the Internet Archive that can be retrieved.

If anyone remembers sites where Nvidia BIOS files were located I can check it out. For an example, it looks like there's a really complete archive of old ATI Radeon BIOS files here on an archive of Techpowerup:
Files: http://web.archive.org/web/*/http://www.techp … erup.com/bios/*
Metadata: http://web.archive.org/web/20060203053430/htt … werup.com/bios/

I didn't notice your link either, that's interesting - here's the full lot of what's archived: http://web.archive.org/web/*/http://driver.ga … n/Nvidia/Bios/*
To get them all, you should check out Wayback-Machine-Downloader, I use it through WSL2 and a 2-day old fork of that code fixed a problem so it's now super useful for downloading huge numbers of files from the archive.

What card do you have? I have a couple of the low profile Gainward MX440 cards but they're probably not the 8x ones and may even be MX440-SE

Yes, I've seen the Gainward BIOSes, unfortunately they are not "late enough" for my case. My Gainward is the GeForce4 PowerPack! Pro/600-8X, the one with 64 MB of 128-bit memory.

I'm trying to make some cards compatible with my new display (Lenovo P40w-20, via DVI to HDMI), because they boot with a "black screen". I think I've pinpointed when nVidia cards started to be "more compatible", but sadly I can't find a MX440 8x BIOS young enough for my 2 cards. I've only had success with a no name FX5200 which I've flashed with another generic but late FX 5200 BIOS, and it started to work right from the POST screen.

I might try a MX4000 BIOS later, though I doubt it will work, since these had a 64-bit memory bandwidth and with a 64-bit MX440 I've seen only 32 MB RAM on my Gainward.