After supplies all but vanished over Christmas, hopefully because Sony Japan was hogging stock for its own big sales (almost 200,000 Vitas sold in six weeks), a new western-model Vita might be slightly less unicorn-like now.
Options are Amazon third-parties (semi-regular stock) eBay or second hand stores (check for scratches). But perhaps the best option is to grab a Japanese model, commonly available new from many importers (on Amazon, eBay and more), and live with the UI X-O button crossover.
I'll update when time allows. Do shout/comment if you spot a new Vita on sale anywhere.
UPDATED: 22 March
UK/EuropeAmazon UK has Vita systems at £198 (up £10 on last month) fulfilled by Bargain Games UK (better than the Italian source from recent months).
Argos has no Vita consoles, but some games onsale.
Smyths Toys stated they weren't getting any new stock in, after selling out over Christmas!
GAME has some pre-owned stock, at least you can check it out in-store, unlike eBay.
Amazon DE has PS Vita Lego MegaPacks (7 left) for €299.
Game Spain has PS Vita Star Wars Lego bundles for a bargain €195.
EB Games AU has pre-owned stock.