There are various types of portable clothes rods, clothes hanging systems or hooks that you can use in some places; but installing them in a truck may be difficult or impossible (depending on what you are allowed to do in your husband's truck, especially if he is a company driver). Trucking companies may not want extra holes drilled in their tractors.
A rod suspended from the upper bunk (either in the vertical or horizontal positions) may or may not be an option for you.
One truck that Mike drove had a bunk-side hole in the cabinet behind the passenger seat and I can envision running a pole or chain between that and the top of the upper bunk when it is closed.
Beware of clothes "swinging" in the back and causing problems with driving. Also, hanging clothes may interfere if the lower bunk is ever opened or the upper bunk is ever lowered.
Installing an "L-shaped" device on the bunk side of any cabinet must be installed such that the upper bunk can clear it.
If you are unwilling to wear clothes that aren't wrinkled, you may have to find (or make) a way to do a lot of ironing in your husband's truck.
There are travel irons that draw little power, heat up quickly and are said to remove wrinkles from just about any fabric, like the one shown.
Unless there is an APU in his truck that has built-in A/C outlets, you will need to first plug an A/C-powered iron into a battery-connected inverter (making sure it doesn't draw more power than the inverter can provide).
Because space may be limited in your husband's truck, bringing a travel-size ironing board may not be an option, so you may need to resort to ironing on the bottom bunk or on top of an "ironing blanket" like the one shown.
The best option in my opinion is for you to consider transitioning your wardrobe to one that does not wrinkle as easily.
I hope that these ideas are helpful. Please let me know how it goes for you.
Mike and I wish your husband and you safe travels and lots of money saving opportunities on the road.