Wings are the same (left and right.) Why add a wing on right when you are adding an extension? Just one more joint to keep aligned. Generally when Uni's (and contractor) saws were sold with right extension tables, there was no wing included.
As suggested, the extension table is probably the least expensive route. If that doesn't work for you, check ebay. There's a seller named ToolsRule that sells Delta parts. This site also sells parts salvaged from old machines :PLAZA MACHINERY,USED MACHINERY, METALWORKING MACHINERY, WOODWORKING MACHINERY.
One last option is to pick up an extension that incorporates a router insert. I've seen them at most woodworking outlets...I know Peachtree carries them. Hope that helps.