The chrome drip tray (9949-451) around the burners is rusted out. how do I find one to replace it. Coleman does not list it as a part

I understand your concern about your 2-burner Coleman stove slipping. Here's an article with a very simple and cheap DIY on how to prevent your Coleman camping stove from sliding. Coleman 2 Burner Camping Stove DIY Non Slip Bottom Traipsing Around

before you injure yourself or worst dont use stove till tighten valve or replacing it

Heaters that have rusted are tin plated or chrome finish, it can be hard to get a stainless steel heaters since some traders sell heaters as stainless steel but don't tell you the burner is made of tin. If you get a new heater just ask the question, is the burner tin or stainless steel? The problem with a burner that goes out can be a simple as changing the thermocouple, these are consumable and last between 2 to 5 years depending on use and storage. But if you have a yellow tipping this is not good, this can be caused by wrong fuel mix or faulty gas valve and is not an easy fix. Found this site very useful patio heater problem solving. Lots of info.

You can find the replacement drip tray at the following link, under "Other Parts",

http://www.appliancefactoryparts.com/gasgrillparts/brands/coleman/9931-750.html

Hope this helped you.

Morgan, unfortunately, it has passed the point of taking better care of it this summer. In addition to replacing the grates, you will probably have to replace the burner(s) and the venturi valve(s), as well as the tray underneath. It will cost you just as much to replace all the parts (if you can find them) , as it would be to replace the grill with something equal to the Road Trip Grill. The accessories you'll need the most are a brass grill cleaning brush and a good quality grill cover (not a $9.99 special).

Sometimes, it's just not worth fixing some things.

If the burner is lighting from underneath, rather than on top, it sounds like the burner has rusted out on the bottom. If the flames are fairly high and wrap around the burner toward the top of the burner, then that's the problem and it will have to be replaced.

The Coleman website has a pretty excellent list of owners manuals. (Here's the link for the 9921A700)
I believe that you unscrew the burner assembly on the right, which will then let you remove the cooktop to clean inside and re-assemble.
This procedure is not listed on the Coleman website or in the owners manual, however it appears to be fairly straightforward. I'd recommend using some teflon tape on the threads when screwing the burner assembly back on.

they are held in place with a screw and they tilt over the venturi tube.

There are lots of good sources for parts. One website that has an excellent part finder is www.repairclinic.com. Whether you decide to buy it there or not, it can help you properly identify the part you need. Note... Westinghouse might also be listed as White-Westinghouse in the searchable list there.

You can remove the frame around the dispenser by pulling it gently and then you access to the screws that hold the dispenser in place. Could be a spillage behind the frame. Good Luck.