My name is Jade, I am with the Social Care Team at Shopify.
While I was not able to find print on demand apps that will print on golf products, some apps such as Printful allow you to print on socks. The closest option that I was able to find for printing on some golf products is VistaPrint. You can view their golf section here.
I hope that you find the print on demand dropshippers that you would like!
Jade | Social Care