How about a custom piece from a maker here:
http://www.bladeforums.com/forums/s...52100-From-3-quot-blade-up-to-almost-14-quot-!
If not that then I would look for a Becker BK14/24. I have the 24 and the D2 steel held up well for my usage as a landscaper. Cutting fert bags, sod, weeding/planting, plastic plant pots, you name it...
though I would suggest a DMT diafold in Fine/Extra fine for field touch ups when needed.
Edit: you don't have to worry about the d2 rusting, pitting or forming much of a patina. I have had mine for over a year and I have done
Nothing to it regarding preventative maintenance, only sharpening it when needed.
The BK14 has 1095crovan steel and while easier to touch up and maintain, it will lose its edge faster in your working conditions due to the silicates in the soil.
If you want something made For You, check out JK Knives. John can make you Exactly what you are looking for in a few different steels.
If you can't find anything that resonates with you, get in touch with John, he will help you out.
http://www.bladeforums.com/forums/forumdisplay.php/830-JK-Handmade-Knives