You want one that is N compatible. That is going to make a big difference. Your lucky though, two adapter happen to be on sale.
Trendnet 647 (20$)Trendnet 687 (60$)The main difference between the two is the signal strength and through put on the N band. Since the DGL-4500 Maxes out at 300 anyway, that doesn't matter, but the signal strength does. 647 broadcast N at 11dBm while 687 broadcast at 13dBm. Is 2Bm worth 40$? For me it was, plus the 687 got better reviews, but unless your going to be really far away from the router, the 647 is a great buy at 20$.
On another note, if possible, can you go wired? Wired is always going to be WAAAAAY better then the best wireless connection. Just thought I would mention it if its plausible.