GoodWill, Salvation Army and other Thrift Shops carry Thread injectors. I found a machine that works very nicely on heavy stuff. Has a few basic stitches built in (no pain in the rear Cams), everything seems to work great, sews silnylon just like it sews cotton. I am very pleased All for under $25.00. The trick is I looked at a lot of rejects before I found a keeper, and my keeper happens to be FOR the Japanese Market.
My expensive Thread Injector, is fussy about what it will sew, the timing gets off, and there are a lot of little things it is touchy about. A lot like my Jag, the machine needs alot of extra care. Not like the old VW, just get in and drive.