I go to my local hardware store that has a huge isle of every bolt, nut, rubber and steel washer and similar pieces in trays. You can buy one or 3 or whatever. One tip - take a pen. You need to write the part# on a little bag for checkout and for some reason they never have a pen around to write down the part numbers. This results in a long checkout as some poor kid tries to locate a needle in a haystack and people behind you start to get pissed. they'll usually find the closest and most expensive thing that looks like it.