I used to shoot with a Sigma SD14 body, and I had a Sigma 18-50mm f/2.8 "macro" lens [the SLD ELD one]. It wasn't true 1:1, but it was super practical because pretty much any time I used the lens, I could get as close as I wanted. (I also had the Sigma 70mm, a true 1:1 macro, for the real close-ups).
I can't even find a used Sigma 18-50mm macro for Nikon on eBay that's not in rough condition. Just seems a little strange? I always loved how useful mine was, and it's not like it had compromised IQ in order to be "macro"--probably the contrary overall. Anyone can suggest an alternative?
Have you looked at the new 17-70mm Sigma? Goes up to 0.34 mag, not too bad:http://slrgear.com/reviews/showproduct.php/product/1560/cat/31
The new 18-35 'A' model is getting a lot of compliments but only 0.23 mag:http://slrgear.com/reviews/showproduct.php/product/1560/cat/31
Have a look on dpr's sales forum there might be some Nikon mount Sigmas there.