Did the Israelites not outgrow their clothes in the forty year wanderings?
Yes, some did but God provided miraculously.
2Remember how the Lord your God led you all the way in the wilderness these forty years, to humble and test you in order to know what was in your heart, whether or not you would keep his commands. 3He humbled you, causing you to hunger and then feeding you with manna, which neither you nor your ancestors had known, to teach you that man does not live on bread alone but on every word that comes from the mouth of the Lord. 4Your clothes did not wear out and your feet did not swell during these forty years.
They always had good clothes on their back and good shoes on their feet because God miraculously provided as he did for their food. They didn't have any trouble finding materials to make new clothes or shoes when needed.
the LORD says, "During the forty years that I led you through the wilderness, your clothes did not wear out, nor did the sandals on your feet.
Ezekiel 16:10 gives us some idea of what sandals were made of:
I clothed you with an embroidered dress and put sandals of fine leather on you.
God miraculously preserved their old clothes and sandals and provided materials for making new clothes and sandals.
The 40 years in the wilderness was one big lesson in God's providence.