If you want a one piece neck, I don't recall seeing one from warwick, and as stated above, most manufacturers don't do them. If, however, all you're looking for is a neck of just one wood with no stringers or laminates, that they do. Most, if not all, standard bolt on models are mad this way. My Streamer LX is a three piece Ovangkol neck, no laminates between. All the corvettes I've owned, as well as the thumb bo I owned and various thumb bo and fortress models, all had either an Ovangkol or Wenge neck with nothing else. Neck thru models I haven't seen, but I'm sure the custom shop could do it without issue.
2006 Warwick P-Nut II #21
2008 Warwick Streamer Stage II 4