If you want a Randall, contact their sole dealer, AG Russell. My wife got a Model 3 made for me through them in 4.5 months. Took a couple more months to get a left handed sheath made by Randall. Paid a bit more than if she had ordered directly from Randall though.
If you are looking at a fixed blade, see if you can find a Hattori HA-6 (Medium Fighting Bowie).
I got mine for about $130. This is one of the top custom knife outfits from Japan. I put my Hattori nearly up with my Randall.
I sent my Hattori to Sunrise River Custom Knives to have them make me a left handed sheath. At the same time I had them replace the leather washer handle with one of black canvas micarta, sanded to a 120 grit finish. This made a handle that is impervious to about anything while providing a nice tacky grip.
You can see this knife on their website on their "custom" page...