I recently bought a Kona Unit, primarily for winter commuting. After getting it home, I realized that though there were mounting points on the front fork for fenders, they were conspicuously absent on the rear.

After experimenting for a bit and making little progress, I went back to my LBS for some help. They came up with a solid and aesthetic solution. (Mad props to Phil at Full Cycle!!!)
I've attached some pictures in case anyone else is in the same boat trying to figure out a way to fix a similar problem.

I'm not sure where they got the clamps from, as the closest I was able to find online after the fact were "earthing pipe clamps" (for grounding) or "three bolt pipe clamps". Neither seem to be as thick as the ones my LBS used, though I suppose round clamp might have some advantages. The rubber liner they added should prevent any slipping or rubbing.

Not only were they able to create an attachment point for the rear stays, but through a clever use of spare parts and some dremel work on the rear clip, they kept the lines clean and maximized the amount of clearance to allow me to run larger tires. (2.1" studded should fit with the sliding dropout all the way forward.) By moving the mounting point, it also solved the common issue of clearing the disc brake caliper, without the need for any spacers.

They also made an "extension" for the front fender mount, to compensate for the fork adjusted 29er front end. This allows the fender to sit lower than it would with the stock hardware.

The last thing I need to do is put on my studded tires, then sit patiently and wait for snow!

Sounds like you have a very good LBS and mechanic. Enjoy!

You can get steel loom clamps with rubber cushions in various sizes for about a buck at Home Depot.

https://www.homedepot.com/h_d1/N-5yc1...atalogId=10053

Jandd claims to have stainless clamps, but if you order, you get the same loom clamps as above instead of the ones pictured, at a much steeper $4 plus hefty shipping. I suspect they're not stainless, either.

https://www.jandd.com/detail.asp?PRODUCT_ID=FCLAMP

They look like 3/8" pipe hangers, you can also use heat some flat stock and a hammer to create the same effect. Definitely cool I have the SKS for road bikes

I bought four packages of p-clamps in the electrical section at Home Depot, so I could try and mount the rack that didn't quite fit my CX bike for commuting. Wasn't sure of the size, so got a variety. So much better than the seatpost rack!! And thanks to the BF poster that pointed out the p-clamps for me.

my seatpost rack acts as a rear fender, but I've been riding my CAAD 10 road bike more

The way they used the rear-reflector mount on the front of the rear fender is a new one to me. I'll need to remember that.

Fitting fenders at the shop always takes a bit of time. I actually quite enjoy trying to figure out the best ways to get them fitted and line up.

P-clips are the more common way to go than the hanger fittings shown by the OP, but whatever works, right? Looks solid, and I like the front fender drop-hanger solution. It's similar to what I've done on my Cross Check turned commuter, to get a clean fender line with 32mm tires (since it can clear a big-ol pair of 45s). I used a piece of strip steel from the hardware store, chopped it down to size with a Dremel and drilled mounting holes to attach it at the fender bracket and the fork crown. Gotta do what ya gotta do, sometimes.