another tidbit, many of the knockoffs of the Comp Tac/Crossbreed style use very thin, inexpensive metal belt clips. While these are perfectly functional in most cases, they can and will scuff a nice leather belt. Comp Tac's clips are heavy-weight vaccuum formed kydex that won't scuff leather and hold up relatively well (though they are not "life time" products - you will need to replace them as they bend, stretch, wear out over time). other solution is to cover the metal belt clips with heat-shrink rubber tubing (like used for electrical applications). Or third solution is to use leather snap belt loops (comp tac, tucker gunleather and others offer these)
If you're set on starting with OWB covered by a loose shirt, then I'd strongly recommend the Wilderness Tactical web belt (infinitely adjustable tension buckle - not limited to certain number and distance of buckle holes like on a leather belt). And as previous post stated, as long as you're not showing your belt it doesn't need to "match" anything, just be functional.
Many of the "police" brands make good leather OWB pancake holsters ... Bianchi, Galco, Gould & Goodrich, DeSantis, Blackhawk, Safariland, Don Hume, etc. This style of holster is used by a lot of plain-clothes police detectives.
In addition to Raven Concealment, take a look at kydex OWB holsters from Comp Tac, Blade Tech, and Atomic Dog (also big list of other similar kydex products here http://www.ar15.com/forums/t_5_23/94097 ... tml&page=1
And of course there are always the super-expensive super-high-quality custom-made products from makers like Tucker Gunleather, Milt Sparks, Alessi, DM Bullard and others (some previously mentioned in this thread)