Having you own knife made? Yeah, not all that uncommon, but it WILL cost. Figure fixed blades starting at around $150, and folders about double that
Go over to bladeforums.com, and look around
Now - once you start looking into "custom knives", you'll find there are really 3 categories
1)"Spec Knives" - these are really one off, or VERY low production knives made by custom makers - their "standard models"
2)Customized to suit - one of the builders takes one of his standard designs, and put what feature you want on it - be it handle materials, blade steels etc - or one of his "standard" designs with only slight changes
3)Full up customs - YOU design the knife, and send drawings to the maker - he talks with you about your idea, and you work out how to make it, and any necessary changes
I own one of each of the above categories - categories 1 and 2 are probably your best bet - find a maker who makes almost what you want, call him, and say "hey, I like your knives - would you be interested in making your model "XXX" with the following changes?" He'll tell you yes or no, and what it'll cost you, and how long you'll wait
BTW as for "wait" - some of the top makers out there have long ago stopped taking orders - some have/had backlogs close to a decade. Waiting 3-6 months is considered 'short"