Serious answer: ask her if she knows of any marriage-worthy women. Tell her to be specific, because she'll try to give a vague answer like, "they're everywhere, you just have to look." Tell her you want her to give you the first and last name of a woman that she personally knows who she feels is (a) looking to get married, (b) suitable for marriage, in your mom's opinion, and of course (c) willing to consider you as a husband.
The purpose of this is two-fold. First, it forces your mom to take a realistic look at the situation. Your mom has friends with daughters your age, or your mom goes to church or whatever - but she takes for granted that there are women out there available for you to marry. But if she actually starts thinking about it, she's going to realize, "oh yeah, I guess my friend Stacy's daughter isn't actually a good candidate because Stacy gossips to me all the time about how her daughter is a slut running around with 'bad boys' all the time." And "hmm, now that I think about it, that 'nice girl' at church does have three kids by four different men - I don't want my grandchild to be 4th place in its mother's mind."
The other purpose of this is, quite frankly, to highlight the fact that your mother has failed her duty. In past generations, older women understood that they had a responsibility to educate young girls so that they don't become degenerate whores, and to vet and introduce suitable women to their sons. I'm not kidding. Used to be that any woman who wanted to get married knew she had to pass the mother-in-law's approval. But today, your mom just sits back as the world burns and then has the gall to ask you, "hey, how come you haven't married yet?"
She's fucking clueless about the situation you're in. Give her a red pill.