|Here are some places you can buy
appliance parts on-line.
I ordered a part from this website in June 2013. They were pleasant on the phone shipped promptly and had the best return/replacement policy I've run across.
I list the following without recommendation.
http://www3.sears.com/ Never buy a part from Sears online unless you can't get it anywhere else. I ordered a refrigerator part from them. When it hadn't arrived in a week, I called. I was handed from person to person, holding in queues for each person. Thirty minutes of waiting later I was told the part had been shipped. When I insisted they tell me when it was shipped they changed their story and admitted it had not been shipped. When I tried to cancel the order they refused. Based on what they told me, it normally takes them 5 days to ship. I ordered the part from another place who shipped the same day. The Sears item arrived 3 weeks after the order.
This one has parts lookup and repair manuals online.
The following places claim to help you with troubleshooting and part number identification.
http://repairclinic.com/ I asked this place for help finding a part number for my failed air conditioner indoor fan relay. When they didn't reply in two days (other than an autoreply form letter saying they'd answer within 24 hours), I sent a follow-up with my case number asking if they intended to help me. They never bothered to answer either inquiry. I won't be using them again.
http://www.easyapplianceparts.com/ This place was cheaper than the one immediately above for a Jenn-Air range burner switch, but that was a few years ago.
The following place sells parts for gas grills
There's an off chance you can find your part by putting the part number in a few internet search engines (like google.com)