Dear Tweety,I’ve got a date with a tomcat and nothing to wear. Sufferin’ succotash! SylviaDear Sylvia,You silly puddy tat. Try Leisure Birds, a teensy-weensy, brand new secondhand shop on the edge of the Mission. You’ll find affordable wardrobe updates: tops, skirts, and dresses, most for under 30 buckawoos.They’ve got some weal finds: like a gray Calvin Klein shift, belted Celine sweater, and printed blue and white 7 Diamonds shirt. There’s even a selection of men’s plaid button-downs and accessories like boots, ties, and flats.Organic decor like deconstructed umbrellas and branches pwetty up the place. If they ask how you found them?Just say a wittle birdie told you.Leisure Birds, 3412 22nd Street, at Guerrero Street (415-550-6911).