YAY!!! Another dual cpu thread! Welcome to the party!
Slot-2 is just the big daddy of Slot-1. In most cases, what you know of Slot 1, also applies to Slot 2, in more or less the same way. The major caveat is comparability. While there are 100's of different manufacturers of slot 1 boards and products, there are only a half-dozen (ish) of companies that ever made slot 2 stuff. There are many many minor pitfalls you can snag on when you venture into the workstation/server world. Worry not, i'll be happy to help however I can.
That is 100% the MS440GX, it is the most common white-box style dual slot-2 board. When I say white-box, It's a server term, and its basic meaning is a server that you build yourself from standard parts. So to answer your other questions in order...
All Slot-2 (and slot-1) boards do require a mounting bracket. DOUBLE so for slot-2. Just look how big those heatsinks are! A lot of the OEM manufacturers designed the chassis to hold the processors upright, so there is not exactly a glut of spare parts like Slot-1. White box solutions are just as bad. As far as I can tell, every manufacturer used their own special brackets, even if they're 99.9% identical. You have three practical options as far as I can see.
#1: Wait on ebay for someone to sell a set of mounting hardware, or more likely a whole 2nd board that includes it. As common as that model of board is, it might not take long.
#2: 3D print a replacement. It should be relatively simple affair. Intel used to be really good about giving out very technical information. I'm willing to bet the drawings exist somewhere.
#3: buy the spare set I have. be warned, I don't know where it is at the moment, and it might not be the correct one, but my brain tells me I own a set of brackets. Somewhere
As a stop-gap measure, I'd check and see if a standard slot-1 holder will fit. It will at least let you play with the board a bit for testing.
Since I'm curious, what processors do you have? Is that image the exact one you have? What are your plans for it? I hope they include Windows 2000 or XP.
It is a mistake to think you can solve any major problems just with potatoes.