Ken,
About 1 year ago, the LH tail lens assembly (p/n 16501873 gp 2.682) was available from gmpartsdirect.com) for about $75 (does not contain the black insert trim). The right side (p/n 16501874) was discontinued and was going for at least twice that....I may have this reversed (LH discontinued but RH available). I now see that both are no longer available at gmpartsdirect.com. I just tried nos4gn but cannot connect due to a server problem. They may still have them and you should look at that site for cost.