Easy enough to find, OCW make them (http://eshop.macsales.com/shop/SSD/OWC/Aura_Pro_Air_2012), just expensive, so best to buy a big enough SSD for your needs when ordering. I went for the 256Gb SSD for my 2012 MBA, which seemed the sweet spot size/price-wise. The one I got was a Samsung unit.
The toshiba sandforce drive is fine and as speedy as the samsung. It's inferior when it comes to filevault and possibly if you time the transfer bar when copy/pasting media that is already compressed by container/codec.
My understanding is that there's less of a performance difference between this year's MBA's SSD brands, each having pros/cons, whereas in previous years the Samsung was much better.
People have been finding significant differences in the brand of display used, though, with Samsung generally considered to be better than the LG display used in some 2012 MBAs, though the difference can be mitigated to an extent by not using the stock colour profile.
I have Samsung for both my display and SSD in my mid-2013 MBA, but would've been happy enough with a Toshiba SSD this year, as don't use FileVault.