I wouldnt be too wedded to the idea of coveralls. I found them uncomfortable when you start sweating a lot because they no longer fit exactly right and they become difficult for head calls. What I did was to buy about 3 sets of old clothes from a salvation army or goodwill. When I was getting off my ship at the end of sea year I just tossed them. I learned that from an engineer who did that every trip so he never had to fly with a bag of clothing.
I did have a pair of clean coveralls for the evening after we knocked off. Had to maintain the engineer image you know.