I'm not sure if this counts as a way, but, you may find a coconut washed up on your beach. Plant it, and grow it into a tree, and you have fruit to sell. Although, currently, I am in the experimenting stage of this process, and I am unsure of the price of coconuts.
Another way to get foreign fruit is to write a lketter, just a sentence, not full of garble like jkudkhfd, and send a seashell as a prtesent, I believe you should get fruit back.
Actually any fruit that is not common to your town sells for 500 bells. You can go to other peoples town, write a letter to a animal (I sent our town fruit, the orange) with a gift that is common to your town. And proboly the mom thing, I just haven't gotten any letters from her yet.