60k is on the short side but not ridiculously so. Books are most economically viable at 80-100k because they are thick enough for buyers to feel they are getting their money's worth. Buyers are put off from paying as much for a slimmer volume even though production costs are similar.
However, padding it out isn't a good solution - a decent reader can tell when a passage has been added as an afterthought. If your story is all told at 60,000 words a good editor would certainly notice that a quarter of what you submit is not adding anything to the plot. Maybe a 60k word story is the right length for this work?
Without knowing your style of writing or talent level it's difficult to judge but would you consider, rather than trying to stretch your 60k story to longer than is comfortable, writing a second 40k word story that runs in counterpoint to harmonise with what you have written so far, and intersperse the two? This takes some skill to get right but could work in some circumstances.