Off the shelf?

For the SLI bridge, you can construct it out of a floppy cable. Instructions can be found on the VOGONS Wiki.

As for pass-through, a monitor extension lead (male - female) would work. As would a VGA switch box, or just changing the connector each time you play in 3D. But that's a pain, as often menus are displayed in 2D and so on.

Your in luck, I just came across some old notes this weekend on this and kept it as someone else asked about a month back.
pass-through search ebay for VGAEXTAA6IN which I discovered from this post
Voodoo passthrough cable

SLI, the floppy hack is probably your only choice but isn't hard, I was surprised mine worked on 1st attempt.

...now to find that other post

You can buy SLI cables off of ebay for around $10, here:
http://www.ebay.com/itm/131503503005

That's what I used for my V2s, and it works well (it's a fairly heavy cable with nice connectors).

Basically any quality VGA cable can work for the pass-thru - I'm using a Monoprice one with slim connectors and ferrites on both ends, it cost a few dollars and I've had no problems with image quality even at 1080p60 or 1024x768 @ 100Hz from the 2D card. I've used shielded 6ft extensions as well without trouble, aside from the weight on the card, and the 6ft of thick cable hanging off the back of the system. 🤣

If your monitor has multiple inputs, or you have a switch, or don't mind being the switch, you can just hook up the master Voodoo2 separately from your 2D card. Given how well my V2s (mine are Creative cards though; no idea if there's any significant difference to Diamond these days) have handled higher resolution on pass-thru, I don't see this as being very necessary, but it is an option.

For drivers, I'd go to falconfly.de or 3dfxzone.it - personally I've had best luck with the 3dfx reference drivers, and have not had good experiences with third-party/"x3dfx" drivers.