BECOME Y2K-FASHION READY FOR UNDER $100.

Byline: Barbara De Witt Fashion Editor

'Tis the season for cheap chic.

When you've blown your budget on gifts for the family and don't have the cash for a haute holiday ensemble, there's no need for a Cinderella complex.

You can kiss the old century goodbye and party into the new one in the season's latest look - the ball-gown skirt - and all the glittery trimmings.

For under $100.

Naturally you've got to lower your expectations a tad, unless you stumble over a designer ball-gown skirt at Marshall's or T.J. Maxx. And it is possible.

But hey, the countdown has begun, and you're in a hurry. So we scouted around, and here's what we found for less than $100 at Topanga Plaza in Canoga Park and Fallbrook Mall in West Hills.

Sears - Two very wearable choices. In the women's department, they have pink (or baby blue) ball-gown skirts in iridescent organza by Apostrophe for $24, and matching beaded sweaters (long sleeves or shells) for $20.40.

In the junior department, near all the embroidered jeans, is a billowy black tulle-covered skirt for $30, paired with a silver lame halter top (the trendy backless type) for $16.

Next stop was the shoe department, where there is a huge variety of evening sandals, but the most fashion-forward are a pair of medium-heeled slides with a choice of silver, black or plum sparkles for $38.

Evening-bag styles were limited here - but inexpensive. A shiny silver clutch was $10.

Rampage - This is a junior-minded store for smaller sizes, but you'll find the hipster version of the ball-gown skirt in crinkled organza in the top three colors of gunmetal, garnet and white. They're $38 each and looked fab with a silver knit halter top for $26.

Shoes and purses for black-tie galas weren't on hand, but we found gunmetal and garnet lace stoles with heavy fringe for only $24 each.

Cathy Jean - This is cheap-chic headquarters for shoes, and we zeroed in on a pair of killer high-heeled sandals in a choice of silver, black, red or garnet for $59.

Forever 21 - We spotted a huge selection of the season's must-have skirt, but the pink iridescent organza number was the best, especially when teamed with a slightly darker pink sequin tube top. Skirt, $27; top, $20.

Party shoes were the clunky variety that teens adore, priced at $16 each in basic black.

Charlotte Russe - Lots of glam gowns for bigger budgets, but way in the back we spotted a pinkish red crinkle-taffeta ball gown skirt that comes with its own black velvet tank top for $79. Unlike the other skirts we scouted, this style has an elastic waist, which could add a few inches to one's figure. On the other hand, it could prove more comfortable.

Shoes are basic black with a bit of silver glitter in hefty platform styles, priced at $28.

Montgomery Ward - There's not much of a party mood here, but the women's department has a tasteful ball-gown skirt in black organza that's accented with tiny embroidered flowers and pearls near the hemline. And there's a matching V-necked sleeveless shell top in white or garnet. Each was $29.99.

JC Penney Outlet - No Cinderella skirts, but some nifty 2000-themed black velvet evening bags with embroidered champagne glasses for $19.99 and matching pumps for $9.99.

New Image - At this shoe store, we found very bare high-heeled sandals in silver with a sassy ankle strap. Priced at $28.

Fashion Mania - It's a stretch to call them ball-gown skirts when they're really more A-line, but the black iridescent skirts were a bargain at $13.99. Silvery tie-back tops for super slim figures were only $11.99.

Claire's Boutique - This accessory shop has lots of rhinestone and crystal bead costume jewelry, but the hottest seller for the holidays is large rhinestones to be snapped or twisted into the hair for $6. Few are wearing long gloves this year, but this store has them for $15.

Mervyn's - No ball gowns or full skirts, but the shoes and handbags were very luxe-looking for the price. Best designer knockoffs were a pair of elegant silver sequin sandals by Hillard & Hanson for $38, and a garnet-colored evening bag in iridescent organza with a crystal-beaded handle. The bag, which is large enough to hold a small wallet or a pair of glasses, was priced at $14.39.

Other bargains at Mervyn's included organza stoles in silver for $19.99, and rhinestone tiaras for $6.