How long is he at work?
With my DH if he's working an 8hr shift- he just eats right before he leaves, takes one meal with him, and eats when he gets home (unless he's going straight to bed- which he usually doesn't do right when he gets home).
However, when he's working 10+ (up to 18hrs sometimes!!!) shifts- he takes more meals than just one! Usually 2 meals and some "snacky" items in case he's hungry for more than those 2 meals.
He uses the divided long narrow tupperware container things (LOL) and just puts meat in the middle (depends on what meat he wants), his veggies that he takes to work are usually either green beans or spinach (frozen/microwavable), and usually some tomato and onion slices- sometimes a hunk (1-2oz) of cheese. If he takes 2 meals- they'll both be like that. The "snacky" items are another container with some cheese in a ziplock baggy, boiled eggs, and recently even took some vienna sausages (the jalapeno kinds) with more slices of tomato and onions or maybe some peppers he's "pickled" himself.
He has his meal with 2 cups salad when he's eating at home. Although sometimes if he didn't eat his salad at home he'll even put the salad in a baggie and he eats it with vinegar which he keeps some at work- so he just took the salad, baggie with cheese in it since he likes to eat it on the side- not grated on the salad, and used the vinegar to have his salad at work with that meal.
I'm not sure if your husband has a place to keep things cold though? If not, that might make it a lot harder!!!
Other snacks that might not be the greatest (because processed meats tend to be higher in sodium and/or nitrites and can cause stalls on weightloss- but then again don't for others and some men especially will probably do fine with them in moderation) would be things like slim jims or other "meaty" snacks that won't go bad if they aren't kept cold- ie: kept on his person so he can snack on them while at work without having to go get it from the fridge or locker or whatever.
Sometimes if he thinks he's going to be working a long shift- he'll also take a tiny little container (about 2 tbsp) with natural SF peanut butter in it- with a baggie of cut celery to go with it. Then he can snack on celery/PB when he feels like he needs to.
I also try to make sure he takes enough (like you obviously are doing

) because I don't want him to not eat TOO LITTLE. He can't eat the same as me (and I think he's trying to! I'm small bone structured and only 5'2!! LOL) he's bigger, way more muscular and ofcourse gets way more of a workout each day than I do- at work and at home. His job is very physical. If he skips meals or doesn't eat enough it might not only slow his weightloss but just plain not be healthy for him and make him weak/etc. He's eating under 20 carbs because he's not much of a veggie eater (which is why he eats the tomatoes and onions too because he has way plenty allowance on carbs to do so -and still stay under 20 carbs) but I still don't think he's eating enough. I did fitday on him one day recently and he'd only eaten 1800 carbs! I really don't think that's enough for a man of his size- which really is mostly muscle! He doesn't have all that much to lose in fat. So I'm trying to get him to eat more.
I hope this helps in some way!