Unfortunately, I've not found many refills that bridge the gap between the cheap Cross styles that come in kits and the real Cross brand refills (unlike Parkers, where there's many good options.) That said, I'm not even that happy with how genuine Cross refill write compared to the Parker.
Amazon.com : Cross Mini Ballpoint Pen Refill, Medium Black, Fits Tech 3, Autocross, Compact, Leather Accessory Pens, 2 Per Card : Office Products
Gary's right, though - genuine Cross ain't what they used to be. I've heard good things about the Beaufort Ink refills as an upmarket replacement, but I have yet to try them. For the number of pens I make, I don't write with the damn things nearly as often as I should.