Watch ebay for a Mavic Ellipse rear wheel. Deep rim and aero spokes. Clincher. Second hand track stuff is usually reasonable condition as it only gets used indoors.
For the front you want something like a Hed 3 as Blah said. If you wait until October-ish you can pick up these cheaper once the TT season comes to an end. Still not 'cheap' in thetraditional sense, although if you're willing to go clincher rather than tub you might get more of a bargain.
