That is a gorgeous print. I remember at C2E2 this past year, he didn't have that print available (he didn't think it was popular enough or it was eliminated by process of elimination given the other prints he had. I can't remember which one it was but it wasn't available at the con). I told him that I so wanted that print badly I purchased the print on eBay at the end of the year (paid double the price). But I told him that's why I did it. Cause it was so hard to find that darn print, and it's such a beautitful work of art. Plus it's so darn hard finding prints of either two. Next day at the con I brought the print in a portfolio book (because I was getting the two pages of Batman & Robin Eternal #13 signed by Tynion) and had that print included. Got Peter to personally sign it to me this time.
Do so. Just tell him the truth. You're a fan of the characters and couldn't make the con. Don't do what I did. Not when you can approuch the artist directly.