Y'all are going to be in love if you ever try real ramen.
I've used wild pig tenderloin to make chashu at home. It wasn't fatty enough so I used Glutaminase enzyme(you can get this on amazon if you can't find it local) to layer in pork fat, tie it all up and set in the fridge for a day. Then make chashu via any recipe you find.
Tonkatsu imo, is the best ramen, but that takes all day and then some, so at home I'll usually do a miso broth. Get lots of woodear mushrooms, make some soy soft boiled eggs. The noodles are key. Don't use dry noodles from a pack. Go to your local Asian grocer and get fresh noodles. They freeze, so don't worry about a pack being too large.