Well, one such case happened to me just yesterday.
To save the $25 checked baggage fee, I left my $4k guitar home and a friend in Pittsburgh loaned me his Peavey Wolfgang for my gig there Sat. night. While changing the strings Sat. morning, a bolt broke off of one of the bridge saddles. It's about a $10 part, but it was a show stopper, since you can only order them online. Another guitar I had mailed him years ago had an acceptable part I could use to get through the night. See missing tooth-like photo below.
Though the broken part was a ticking time bomb and would have happened on my friend's watch, had he changed the strings before I did, I felt obligated to fix it before I left town. To get the broken bolt drilled out we tried a Midas, a Meineke, a welding shop, a transmission shop and the local Guitar Center before finally finding a machine shop that said they could do it. Yesterday they called to ask me to bring down a good bolt so they'd know the correct size and pitch of what they were drilling out. We probably drove 50 miles, spent three hours and the bill was $50 to replace what I probably could have ordered online and had overnighted for less. But I got it reinstalled yesterday before I went back home.