Do you have a Singer dealer nearby? That would probably be the best place to get one. But it might be cheaper to find it on ebay or somewhere online.
I have a Bernina 800DL serger that I LOVE!!! I have a home business where I sew 4 layers of Jersey knit without a hitch -- which my old White serger can't do. They usually sell for around $899. It has differential feed and a built-in rolled hem. But it doesn't have an air threader or needle threader, but is a real work horse. After you thread it 3 or 4 times, it's no big deal.