Couple things to think about:

As someone who does exactly what you envision, I find that the Blaklader kilt is very nice for this. One thing I like about it for this purpose is that it's constructed with the "pleats" sewn open. This means that while it's more like a canvas skirt, it also allows more air circulation and less chafing from pleats swinging against sweaty legs. Blaklader only has buttons at the waistband, and a nice wide apron that stays put even in moderate winds.

It has four huge pockets in front that are great for holding wrenches and irrigation system parts while you're working as well as hammer loop and small pockets for pencils and other necessities.

If you're going to be up on a ladder or roof around impressionable persons, it does not have the "modesty snaps" that UK puts in their Workman. If that's an issue to you a couple of minutes' work with a pair of snap pliers would remedy that lack. On the other hand, it's a farm. The ram doesn't seem bothered by having the boys swing in the breeze so maybe we're being too sissy.

They run about CAD$140 and can be ordered through any outlet that carries Blaklader's regular line. From experience, a 38 waist is about a 36, so order a size larger than you think you need. You get either black or high-vis yellow.

The other thing to consider is a bespoke kilt made with such options as you require. More expensive, but you get exactly what you want. I really like what Freedom Kilts can do in that line.