Reddit mentions of Sunrace SL-R96 Shifter Sunrace Hb Barend Slr96 Rh 9s Bk/sl

The big thing about converting to drops is that they can add a lot of reach to your riding position. The second part of this guide can give you a good rough idea of whether you might need significantly more or less reach than you currently have, which you can adjust a little bit with different stems.

http://www.wikihow.com/Size-a-Road-Bike

Ultimately it's generally a lot of trial and error though. And it seems your bars are already 31.8mm so you might actually be able to use the same stem. At least for now.

I have absolutely no idea how much those origin8 parts would cost you. But you can probably get the bars themselves for less than $40, eg:

http://www.performancebike.com/bikes/Product_10052_10551_1033658_-1_400213__400213

http://www.performancebike.com/bikes/Product_10052_10551_1184245_-1_400213__400213

The main thing is the width, which largely depends on what sort of bike sizing you have and how big you yourself are, but since you're coming from super wide flats you could probably stick to 44cm regardless. The other difference is shape, which is largely personal preference. Doesn't help you much, but depending on what you want to use the bike for a shorter drop might be more comfortable. And at some point you just have to make the call on what looks most comfortable to you.

Your disc brakes are linear pull, which means it probably wouldn't be a good idea to use normal road levers with them. Tektro do a set of linear pull road levers which would probably be the simplest solution:

http://www.tektro.com/_english/01_products/01_prodetail.php?pid=10&sortname=Lever&sort=1&fid=3

Pretty cheap too. Shifting is a little more awkward, as your thumb shifter will probably have a diameter of 22.2mm and modern road bars are generally 23.8mm. But that shifting position itself is generally pretty awkward, yes. Your hand has to move quite the distance from the hoods or the drops to get there, around the bars themselves and often requiring you to change position. Short of using a road lever with a cable pull adjuster or something, which can get quite complicated and isn't generally the best, the best option is probably a bar end shifter. Something like this:

http://www.amazon.com/SUNRACE-SHIFTER-HB-BAREND-SLR96/dp/B00JVK5ZLY/

So all in all that'd be around $40 bars, $25 for the levers, $35 for the shifter, $10-15 for some bar tape and maybe $15 for a new set of cables;

http://www.amazon.com/Shimano-Brake-Cable-Housing-Universal/dp/B0050LUBZ8/

Basically something like that plus a new bit of gear cable outer, to cover the distance from the shifter to the first boss on the frame. Probably cheapest and simplest just to get something like that from an LBS. But all in all that'd be around $125-130, if you're lucky and it's comfortable as is. If you need a stem with a different length or angle, probably closer to $150. If you do the work yourself. But for that you could end up with quite a nice gravel/adventure type bike which could turn its hand to endurance road riding, cross riding or touring/commuting quite nicely.

Alternatively you could just get some bar ends, which can help even if your arms are quite spread out. But if you want to get into longer distance riding, you might feel the need to upgrade again before long. Bullhorns can be nice, but often have a lot of the same problems with different diameters, and you still can't brake from that position unless you had TT style levers which I don't think you can get in linear pull. And they'd still need bar tape and such. You can do the research yourself, I just think it'd be a large portion of the investment in an attempt to mimic the riding position of a road bike anyway.