Spearra wrote: The Cougar Vantar is about $33(ish) in USD. It is very low profile and isn't the monstrous price of a BFKB113PBK (which is near $100 USD).
If you want something a bit more durable than the C.V. at the cost of the keyboard's keys being about 3.8mm high, the Perixx PX-1900 is about $40 USD. The rebound is a bit violent in the case of the PX-1900 so it feels heavier then it actually is. The PX-1900 is severely underestimated build quality wise. It takes about 50+/= grams of force to actuate.
Basically: (In USD) Cougar Vantar is about $33, flat but basic,
the Perixx PX-1900 is about $40, which is more durable but is hilariously thick for a scissor switch keyboard,
and finally the BFKB113PBK which is a unrealistic near $100 range. Pretty much combines the prior two, the flatness of the C.V. but the durability and reliability of the P.PX-1900.
If you really need the flat design, go with the Cougar Vantar. If you can tolerate the extra height of the Perixx PX-1900, the extremely good build quality of it is a easy recommendation on my end. But if you can afford to do so, the BFKB113PBK will more then likely be complete overkill in both departments with it's colossal price (for a scissor switch keyboard).
Oh, and the Perixx PX-1900 and BFKB113PBK are water/spill resistant if that is anything of interest. Along with dust resistance which rubber domes in general are pretty resistant against (that being dust).
Finally, as far as stabilization is concerned, I've noticed the PX-1900 slaughters the other two options. From a sitting distance, it borderline doesn't wobble visually so rattle almost doesn't exist. Do note that, as high of a key structure the PX-1900 is, it still has a short of travel that scissor switches are famous/notorious for.
That's just my hilariously bias opinion though! The other scissor switch options besides these 3, I've noticed aren't too great usually because they screw with that bottom row and it destroys the feel of the entire board. Either that or they just outright suck built quality wise. If you go with any external scissor switch keyboard, I highly recommend your decision be of one of these three, since all the others are dodgy at best.