I looked into this briefly, but found that a far better solution for me as a dude, was to just go to work fresh and showered, run at lunch (tons of sweat - I’m still running during high summer heat), and then use a clean bath towel to thoroughly towel off as well as do a quick ‘bird bath’ for the head/neck in the bathroom. Then change into work clothes, apply deodorant. Baby powder can help keep things down under dry as well.
You’ll pretty much be as clean as you’ll get for work and good to go. And much less fuss than a portable shower.
This is probably not the answer you wanted, but when I was in the Peace Corps we had cold water showers at our training center. Which was fine for a quick rinse but not good for washing my fairly long hair.
For warm water, I’d fill a couple of two-liter soda bottles with water and put them outdoors on a piece of black plastic, and the sun would heat them up over a couple of hours. Worked great.
Like I say, probably not the answer for your lunchtime run.
The other thing that works fine is just stash a towel at work or in your car and douse half the towel with water and use it for a quick cleanup and the dry half of the towel to dry off.
It’s not a shower, aka a large amount of water to pour over your naked self, but if you can get past needing that, there are lots of ways to clean up and be presentable at work.
Where are you going to use it? Parking lot? I have used the generic plastic type bag suspended above your head while backpacking. They work ok. Nothing fancy, just running water over you. I think the one I had was 5 gallons. Certainly enough to get the sweat off. I usually heated at least some of the water as it usually came from a cold stream when I was using it, but that probably won’t be a problem for you.
It is just what it says. If you want warmer water, leave the bottles you plan to use in the sun. Buy a pop up shelter like the windshield sun visors and you have instant privacy. You can buy a powered system as well or just get submersible 12 volt pump and dump into a water container.
I use the 2L bottle with water in it all the time. This time of year it will be plenty warm. I usually have one or two in my car for good measure. 1 would be good enough for a quick rinse after a run I think. I use it primarily after OWS to get all the gunk off.
Check this out, may be a little more than what your looking for, but awesome nonetheless! https://www.youtube.com/watch?v=zuAPGVx9vhs
We are planning out our ultimate race rig/basecamp, which will be a converted Sprinter van. This will be our shower option!