disc hubs tend to be fatter…
…and for good reason: they have to deal with higher twisting forces and a larger diameter tube is a good start. so you’re unlikely to find a 6-bolt hub with the dimensions of a classic road hub, certainly i don’t know of any though somebody out there might be able to point you in the direction of one. if you want something that’s clean looking, well made and sturdy, i’d suggest a set of Hope Pro II hubs – okay they’re not super-slim but functionally it’s hard to do better, and you can get nice understated silver ones. As the basis for a touring wheel i reckon they’re just about ideal.