Thank you for the inquiry and for using SearsPartsDirect.com.
This specific model does not have any other side burner options besides what it originally came with. Some models will have kits to have options on the side burners such as griddles or coils, ect. but this model just has the one option.
Sears doesn't recommend altering the grill beyond what the manufacturer offers for the model, but I think it would be feasible to fabricate another set-up in if you are handy enough and locate something that will work. However, the manufactuer doesn't offer anything for this model as far as additional accessories, so any modification and research thereof would need to be performed by the owner.
Sorry I couldn't give you better news on the side burner or accessory and wish you all the best with the grill. Thanks for using SearsPartsDirect.com.