Repairing a Tzitzit Shirt

I have a very comfortable military Tzitzit shirt that I really love, but the strings have worn out. The Rabbi told me that it is forbidden to wear it without new strings. The problem is that in my area, only ready-made Tzitzit are available. And even if I could buy the strings, I don't know how to tie them, nor do I have anyone to tie them for me, and I also don't have the patience to learn how to tie them. Is there a way that I can still use this shirt?

If you sew the ends together so that the shirt ends evenly, with a permanent and stable seam, and in fact, it is enough that most of the garment is sewn together, even if part of the ends remain, you can continue to use it without a problem. You can also round the corners of the garment, that is, cut one or more corners so they are round-shaped for 10 cm, and then there is no obligation to attach the Tzitzit strings.

Shulchan Aruch (Orach Chaim, Chapter 10).