Your conditions are probably too cold for ampullaria (extreme lowlander,) but might be ok for a talangensis. However, my talangensis only seem to produce a lot of pitchers when it's very cold, so you may run into some frustration there.

If you're really into round, squat pitchers, I'm a huge fan of Nepenthes spectabilis 'Giant' x aristolochioides. They are much easier to grow and more robust than N. aristolochioides, but they maintain the characteristic shape.

Here's a pic:
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How about N. viking / globosa:

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Thanks, I'll look into those two. Peter from California Carnivores suggested "the beautiful and squat N. x singapore tech" They are conveniently selling it at this time! lol