Now, instead of a rock barrier, there are metal "heat tents," which are angled pieces that fit over the burners to prevent drippings from reaching them. This channels the grease down through the grill into a collection pan. When done correctly, this reduces flare-ups and as many purists will tell you, also reduces flavor. It is for this reason that I have received a continuous stream of inquiries about lava rock grills and where to find them. The answer is that few grills are made with any kind of rock barrier and those few that are, tend to be very expensive.
So, what do you do if you want to go back to the good old days of the lava rock grill without buying one that is 20 years old? Converting a gas grill to lava rocks isn't difficult. Two things to know before you do. First, modifying a grill can void the warranty, so be aware that getting replacement parts can be a problem if you make changes. Second, converting from heat tents to lava rocks can lead to more flare-ups, so don't discard the heat tents in case you need to switch back.
Fortunately, converting to lava rocks is easy. All you need is a metal wire grate that fits the grill and a bag of lava rocks. Remove the metal heat tents or barrier the grill came with. Fit in the new grate and evenly distribute the lava rocks. The rocks need to be left enough room for air to flow through, but cover the burners to protect them from drippings.
The trick is to find the right sized grate that will fit the grill body between the burners and the cooking grate. This should sit on the brackets that hold the heat tents in place. Chances are you can find the grate you need online by measuring the grill body and doing a search for grill grate and the measurements. Many stores that sell grill parts might have just what you need in stock for under $20USD. GrillPro, one of the Onward Manufacturing Companies, makes a universal fit rock grate that fits most sizes of gas grills.
Of course, you don't have to use lava rocks. There are a number of ceramic briquettes and tiles (like the The No Flare Square tiles that can perform the same function in your grill. This premise suggests a reduction of flare-ups (I'm not making any promises) and better even heating. So, if you are dissatisfied with how your gas grill cooks, you might want to give this conversion a try. A bag of lava rocks and a rock grate for your grill shouldn't cost you more than around $30USD.