The Nexus 5 isn't being retired just yet, so you can still have the latest and greatest Nexus for a few more months. It seems kind of silly to pay full price for it at this point, though. Luckily, the international LTE variant (D821) is on sale today for $329.99 with free shipping in the US. There's no tax unless you're in Missouri, where it's 8%.
Because this is the international version, it won't have the right LTE bands for US carriers (that's the D820). Still, if you spend a lot of time abroad this is a solid deal. The Nexus 5 is actually more expensive in a lot of countries as well. If the area you'll be in has any of the following LTE bands, this phone will work–800/850/900/1800/2100/2600. The HSPA support should function in the US and overseas.
This is just the 16GB model and you've got no choice of colors. You can get it shipped internationally, and it's not obscenely expensive (about $12 for the UK), but you will probably be stuck with import charges.