Like Walter mentioned, any DVI capable monitor would suit you just fine. Just understand that it will probably NOT be color accurate at all. In fact, you will probably have color differences between the two screens that you’ll be using. Whether or not this matters to you depends on your work, but when I just recently got one of the older Dell 24″ monitors to work with my Macbook Pro, I found it excruciating to work on any photos or do even simple color correction, since the colors between my MBP and the Dell were very different. Of course, whenever you’re doing color correction you should really be using a separate reference monitor that you know is accurate.
Best of Luck,
Glenn Fisher