Going back to the OP, I've been putting the dimensions of all pres with digi-out into a spread sheet.
Looking at which units are smaller than the V3, here they are, arranged from smallest to biggest:
Model Street price Cubic inches
Core Sound Mic2496 599 23
USBPre2 649 47
Echo Audiofire 4 249 49
Graham-Patten DMic-20/24 (disc.) 75 56
Aeta Audio MIXY 2100 62
Edirol FA-66 339 65
Sonosax SX-M32 2716 68
Marenius MM-4220 2100 70
Aeta Audio MIX2000 + AD card (disc.) 1300 75
Grace Lunatec V3 1390 77
...
Audient Mico 660 160
So if the OP wants a quality pre smaller than the V3 without breaking the bank, the USBPre2 is hard to beat for the money/size ratio.
If you're on a budget, the Echo Audiofire4 or Dmic-20 might be an option, but I doubt they have the same sound, and definitely not the versatility...