We are running one of these setups right now. Vitaras and our own rods. The pistons will cost you about $125 from fjt, and the rods are $225 from us. With about $40 in machining, you'll have just about everything you need for a lower compression setip in most D16 engines.
Here is a link to the rods. (back in stock after the holidays, we sold out!)
D16 HBeam Rods as Tuner Toys
Although I am not sure about the D15B VTEC motor specifically, I believe that most of the D15 cranks have smaller journals, so cannot use the rods normally used for a D16 engine. I beleive that there is one company making rods for the D15, but at $700 a set, they are pretty pricey.
I'd find yourself a D16 core at the junkyard, and build it up. Throw on a hone and some bearings, along with the TTRods and Vitara pistons, and you'll have a boost happy shortblock going. Add any D compatible head, and you're done! An easy route is going A6 Block, Y8 Head, Vitaras and TT Rods. The Y8 head brings compression within reason, and accept the Y8 (OBD2) or A6 (OBD0) distributors. Use the Z6 head for OBD1 distributors.
Hope that helps,
Craig