I was VI's correspondent on Blue Ribbon and they'll special order Chiapetti lamb for you, but it takes a day or two. (Steve Chiapetti was the chef at Cafe Le Coq in Oak Park and his family has been wholesaleing lamb in Chicago for I don't know how many years. Answer to come from the wonderful LTH community, I expect.)
Whole Foods (a.k.a.Whole Paycheck) sells the same lamb for 1.5x+ what Blue Ribbon does. You can also order a whole leg or whole lamb from them and they'll dress it for you.
They're really nice guys and they're real butchers. They can roll cut a pork loin to 1/2" thick so you can stuff it with all sorts of goodies and roast it and if you want to buy a whole short loin or other primal, they'll age it for you gratis. Buy a short loin, call 'em up, tell 'em you need four steaks cut two inches thick and pick the steaks later in the day.
If you need frenched lamb racks on a regular basis, Costco in Oak Brook (and everywhere else) has frenched Australian lamb rack from Australia for $10 / pound. The lamb is generally very good and it's one of the few things Costco sells that's sized for immediate consumption by two people...