Go into Knifemaker's market, Folders for sale. Look around for a week or so and you will see the guys that advertise with us. Not all are terribly expensive when they're "on their way up" and make good knives.
Here is some of Joe Hoover's custom work. I've had two of his custom frame-lock folders...both excellent, and both in the $300-dollar range. I gave one to my younger son and he loves it. CPM154 blade, about 3.3" long, titanium slabs. Smooth, tight, nice design and quickly made to YOUR specs.
Of course there are many others. But this is one that won't break the bank...and I've purchased two of his and they're excellent. Here are two pics of one of them...
Here is Joe Hoover's linerlock...third in the listing today.
My preference is a frame-lock, generally, rather than liner-lock, but that's a personal thing only.
http://www.bladeforums.com/forums/showthread.php/1241768-Linerlock-EDC
You could also follow this link to pick up a custom that is pre-owned and usually less expensive. MANY of these have never been carried.
http://www.bladeforums.com/forums/forumdisplay.php/748-For-Sale-Custom-Knives-(Individual)
You could also go for a "mid-tech" which is an "almost" custom from a custom-maker who doesn't actually manufacture the complete knife by himself. This is going to be much cheaper than his real "custom" job, with nearly the same degree of excellence.
One mid-tech that I'm enjoying right now is by Brad Southard. This maker collaborates with Spyderco occasionally and does great knives. His mid-tech is the AVO, which is almost, but not quite, a full custom. This one is a flipper, but is slim, light, well-designed, solid lockup and centered. Whatever, I am loving it. They're generally out of stock on-line, but you can find them here on the Exchange quite often in the $500 range...as NEW.
Here is one pic of mine...riding along with my large Regular CRK Sebenza...
Good luck; have fun. Caveat Emptor!