They are available on amazon for sure.
Many local dog walkers use them at my local park area.
Weirdly, they stared at me blankly when i ask why a group of them why they were spraying their dogs down with water that had been sat in the car overnight so was near freezing..
Our GS Dog, launches itself into mud, no messing full 360 x 10, looks like a food mixer has been thrown in.
I’m not the only one that’s delighted to have an excellent proper butcher nearby ..
2 hours of freedom for me .. a bomb could drop on the house and she’d not desert her bone.
Once she’d finished it .. it took me a while to work out where she’d hidden it. It was in one of my wellies! 
I use one of these at Tinvilla you can set to very low pressure and set it to spray 
It Worx wonders, see what i did there, I’ll get my coat
I have the worx power washer and tried it once it was a pain as lance to long need to carry alot of water in a sealed container to fill a bucket of water and constantly readjusting the pipe to make sure it’s under the water to suck up, unless you’ve got a good dog stand still and will let you stand away and light spray well done but still hard with a lance to get under them properly. Can be ok if cleaning the pooch in the back garden before going in then a garden hose do same job.
This is what I found which is perfect got plenty of nozzle attachment to suit your preference, lance can be short or extended to be long, it’s battery operated only pumps when pull trigger so no battery wastage, it takes up little room in the boot strapped I can fill with hot water and can stay like warm for ages,
Basically finish the walk open boot flick the on switch grab the trigger and rinse, and use car valeting towels as they brilliant for drying a dog. You can comfort the pet with one hand and spray with the other as unlike the worx only need one hand to operate and point.
Been handy for filling up dog bowels and filling my windscreen washer in the past when ran out unexpectedly on a drive.
I use the 12 ltr and enough water to last 4 washers at least but can be weeks sometimes if it’s just dirty paws,
https://greyarro.ws/t/today-i-treated-myself-to-this/8964/11585?u=ziceman
Do you have a link?
With Sophie, her long fine feathering doesn’t really clean with a hose/spray. It’s long enough that it just makes the water run over the surface and never gets to the roots. ONLY a leg-deep tub allows the fur to open up and allow decent cleaning of legs/tail/tummy.
If it me your referring too?
If it’s the worx then I can send you the whole kit free minus the battery as I use them for my other worx tools. 
Yup. Thanks.
For dogs I think a Mud Daddy is the way to go, the brush is great for removing mud on difficult coats
It won’t achieve anything on a mega wet/muddy dog like mine. Her feathering is so long nothing gets to the skin other than being submersed in water so that it all opens up. Even a hose only runs over the sodden fur.
I have one of them. Great piece of kit. My missus fills it with hot water before we travel so mutley has warm water after the walk 
I actually seen them developing it many years ago on TV invention competition show and thought wow why nobody think about this before what a great idea, but I had a garden sprayer already and used this but found it was continuous pumping the pressure up but it was handy.
They design electric doggy ones like karcher expensive 15 mini battery life so basically it was another thing to carry back and forth from house to car on every dog walk, the knapsack has a 5 to 8 HR battery life before charging I can spray holding in one hand and use the other hand to ruffle the fur so to get agitated.
It never been 100% clean but it does help on the boy carrying it dirty onto the carpets/rugs and furniture.
You get mud loving dogs like @OzoneVibe that the only answer would be this hooked on
More chances that I get the hair clippers out and remove ALL her fur!
If the clippers came out she’d be clipped to being mud compatible .. not a hair remaining.
This is what I’m up against … normally a lovely dry stroll in the local country park .. her relentless energy and the ridiculous weather and resulting mud. The worst of the mud didn’t get videoed .. I was struggling to stop myself falling over.
(Just a quick sequence of mobile clips.)
Took almost 30 minutes to wash her .. and now all my clothes are in the washing machine. 
Surely not Dave !!!