N. x Judith Finn (N. spathulata x veitchii) is a possibility. It's not a plant that is typically coveted by collectors, but it is easy and will stay small for quite a while. I had one that I didn't really want, and it seemed to thrive on my brutal neglect. Even environmental changes didn't faze it. It was like a succulent. The leaves on the rosette were thick and fleshy, and the pitchers were lovely, surrounding the pot like tall sentries. It's a nice neat plant while it's still in the rosette stage.

Unless you want to switch to artificial lighting, there is little you can do to promote growth in the winter. In northern latitudes, nepenthes growing in natural light will almost always slow down considerably, even to a full stop, in the winter due to the shortened photo period.