ATLANTA -

When securing supply for their used-car lots, dealers may be having trouble finding enough luxury units this fall. The AutoTrader.com analysis of last month's supply trends found that, once again, vehicles in this segment remain elusive.

According to September’s installment of vehicle scarcity data that is provided monthly to Auto Remarketing by AutoTrader.com, CPO luxury vehicles, in particular, are becoming increasingly scarce nationally.   

AutoTrader's data includes the 10 Most Scarce CPO Vehicles and 10 Most Scarce Late-Model Used Vehicles on a national scale and for each of the top 10 Designated Market Areas.

And what this data shows is that seven out of the top 10 hardest-to-find CPO vehicles in the country are luxury cars or SUVs.

One luxury brand, in particular, is proving to be the most elusive. AutoTrader said Audi's S4 (No. 6), S5 (No. 10) and A8 (No. 7), all made the Top 10 scarcest CPO vehicle list on a national basis.

Topping the CPO national scarcity list was the Honda S2000, followed by the BWM M3 Series in the No. 2 spot.

For the late-model used vehicles, the Scion FR-S is No. 1 on the list, with the sporty Porsche Cayman in second. The BMW 7Series, Hummer H3T and the BMW MSeries, respectively, round out the Top 5 scarcest late-model used units on a national level.

On a DMA level, the “luxury theme” continues, according to AutoTrader.

The Audi S4 tops the CPO scarcity list in Atlanta, Dallas Ft-Worth and New York, and is No. 3  in Boston and Chicago. The Audi A8 is top in CPO scarcity for Chicago, San Francisco and Washington D.C., the company added.

Additionally, CPO Porsche models (Cayman, 911 and Cayenne) remain scarce in Houston.

For more hard-to-find units, check out the charts provided to Auto Remarketing by AutoTrader: