The new mini Iroshizuku ink bottles have arrived! They are 15 mL each, and just as classy looking as the larger size. They come in individual bottles, plus some colors come in a 3-bottle gift set. They are still pricey, as it’s practically $1 per mL, whereas the large version supplies 50 mL for about $30, but it’s still a nice solution for someone who doesn’t want to spend $30 or knows (s)he doesn’t need or want 50 mL of ink.
The cheapest price I have seen is $12.19 (with free shipping!) on Amazon, although it doesn’t seem that all colors are available.
They are also at JetPens.com for $14.00 + shipping (shipping price depends on your order).