I actually ended up just ordering a set off Amazon.jp an hour ago. Got a multi-color denim pack of 25 for about $140 HKD shipped.
I found on Ubuy you can get iron on patches and Tenacious Tape and Gorilla All Weather Tape. I don't know which of these 3 solutions might work best for you though.
Learn to mend with a darning stitch/satin stitch/ladder stitch. Saves you cash, all you need is a heavy duty needle and thread.
From an Amazon Review in 2012
( I will check mine and sell them as vintage, hehe í ½í¸‰)
I did some research (even called Levi) and discovered that about ten years ago Levi downgraded the weight of their jeans from 14.5 oz/yard to 12.5 oz. Why did they do this? For the same reason food companies keep shrinking the amount of product in their packaging.
For one, the thin fabric costs less. Then thinner fabric is easier and quicker to sew. And of course, the jeans will wear out faster and then the customer must buy a new pair.
The old heavy weight fabric was great and I lament the loss. BTW, almost all brands of jeans (even so called designer jeans) are made with 12.5 oz now.
Also, the fit of the STF seems to be different...I suspect Levi has changed them to fit an expanding American male physique.
The good news is that I found a replacement jean. It is called the Unbranded Brand. It is made with beautiful Japanese heavyweight 14.5 oz selvedge denim and is just like the fabric Levi used to use. They are about $80/pair and very much worth it.