Tail Coats

Every once in a while you can catch a good vintage find that comes close. I guess it depends how picky you are about the sequin design and jacket shape.
Most common these days are the 'foil dot' costumes - faux sequins glued onto a glitzy fabric background. A reasonable investment for a starter costume or someone who doesn't plan to perform Columbia often.
Sequin Fabric
If you're dedicated to accuracy you'll want to look for a wavy, skip-a-row sequin arrangement. I've seen the wavy strands attached to chiffon, taffeta, jersey knit and thick spring weave (think tube tops). I am not a fan of using stretchy fabrics for tail coats and the only advice I will ever give on the subject no matter how hard you press me is "no" - not because it can't be done, but because I don't want to be responsible for a multi-hundred dollar failure if you don't achieve the results you wanted.

If you're less concerned with the accuracy, there's still plenty of gold options out there. Sometimes with square or oval sequin, sometimes dangly instead of stitched flat, etc. But for the cost of buying something that isn't right and putting that much work into it, you'd probably be better off buying the Rubies coat mentioned above.
Custom Orders
I'm not currently accepting custom orders - partially because I can't find a reliable fabric source myself, and also because I've suspended all commissions while I'm caring for my mother and trying to move forward with other (non-Rocky) work.
However, there has been some dialogue about having it custom manufactured like the bustier fabric is. The problem, of course, is the huge amount of money that has to fronted by an individual for a bolt of custom fabric. We're talking a couple thousand dollars. Not a big problem if it gets unloaded quickly, but definitely a concern if it takes months or years to recover the cost. It would most likely be in the neighborhood of $60/yd, and take 3 yards to make a tail coat (not including black sequin fabric for the lapels and whatever fabric for the lining).
If you think you would seriously consider purchasing custom fabric in that price range I encourage you to leave a comment to this blog entry. If enough people are seriously interested we could make this a reality. Please, think of the Columbias.