As someone who decided this time last year that I wanted to get a few CPs for the (unheated) greenhouse (I intended to get maybe half a dozen plants, I now have 60 a year later!) I know the problem. If you buy from a proper grower (nursery or seller here), flytraps, Sarracenia and any temperate sundews will be dormant and you will be staring at an active and boring plant for the next 2 months before they burst into life. Some garden centres may have some of these that look nice and growing. Avoid them; these have not been allowed to go dormant and the stress of putting them into a 'normal' season may kill them or stunt them.
Other sundews (like the Cape or Alice sundew) will be growing, albeit slowly, as will Nepenthes. With Nepenthes especially, I would not trust the postal system to be uniformly warm this time of year, and a night in a warehouse at -2 will kill them.
If you want to save a bit of money, you can buy ready made compost suitable for the Sarracenia'VFT/sundews and buy the plants bare rooted and pot them yourself. Look on here and online auctions and you can get dormant Sarracenia at great prices (but check they are adult plants and not seedlings). You can do that now or wait till March-April.