So I was changing the 12V battery in my '07 (thanks, Blizzard of 2016!), and in the process the bolt that secures the exhaust duct to the sidewall fell into the battery well, and my short, stubby fingers couldn't get it loose. At this point I have everything else reassembled so I can drive the car, but I was wondering what I should be looking for in terms of a replacement bolt since I'd rather not drive around with the thing loose for long.
Home Depot sells metric fasteners. Some of the license plate bolts are pretty standard and in a commonly used size, make sure you get the metric size.
IIRC correctly, I did the same thing while cleaning the blower fan. IIRC again, I think I got out the household vacuum cleaner (a shop vac might work, also), and put the skinny "knife edge" crevice tool type attachment onto the end of the hose, stuck it behind the battey and the bolt stuck to the end of the attachement (too thick to go through into the actual hose). There is a slight possibility that I used my magnetic pickup tool, but I doubt it, since that would have entailed me walking up to my tool shed and getting it, and I already had the vacuum next to me since I was cleaning out dust and junk, anyway.
Similarly, you can get tube extension kits for vacuums, best used with a decent wet-dry since it reduces flow quite a bit: Vaccuflex™ - Lee Valley Tools
As an aside, just so it does not turn into a "lather, rinse, repeat," sort of thing, whether you keep buying new hardware or recover the old....smear some white grease -- or even vaseline will work -- on your socket, to help prevent the bolt from slipping off.
I sort of made my own several years ago -- again using the crevice tool and the body of a cheap Bic pen. Took out the innards of the pen, stuck the tube into the end of the crevice tool and taped up all around. Made it possible to get a bunch of seeds out of the blower fan that some rodents had decided to store in there for the winter.
This is a self-tapping bolt since it fits into a plastic fitting in the right rear fender. A magnetic wand may find the original. I use a piece of electrician's tape to hold the bolt to my socket. Once the bolt gets started into the hole, I pull the socket away so that the tape will let go. Then I remove the tape and use the socket to fully tighten the bolt.