How can I replace a broken M.2 SSD mounting standoff for my motherboard?

This is baffling since—if what you are saying is true—the M.2 mounting screw being fused makes no sense; it should simply be a standoff with a small screw in it.

Looking through the official ASUS Z97I-PLUS manual doesn’t help much either. The only thing I can glean from all of this is your motherboard can handle 2242, 2260 and 2280 sized SSDs; 22mm is the width and 42mm, 60mm and 80mm are lengths.

While you state:

I think my best bet is just to order a bag of these online somewhere for 89 cents.

Your point-of-view on the cost of these screws is understandable in broad terms. But I am pretty sure that kind of “89 cent per-bag” pricing is for very commonly available screws; not for odd-ball parts like this.

That said, I would say your best bet to find a replacement is to either successfully get through to someone at Asus who can better help you, or contact a specialty supplier such as LaptopScrews.com and see if they can assist you. And yes, they seem to have tons of screws but no standoffs/sockets. But I am pretty confident a place like that—which has seen close to everything—would be a good neutral source of info that might be able to help you out of a bind like this.