Mechanical fastener to replace zip.
 

I wish to replace a zip on the front of a pair of men's trousers. It is
beyond my skills to sew in a new zip. The trousers are quite old so its not
worth spending a lot of money on them, but they still have some life in them
and are very comfortable.

I have tried sewing in some metal press studs, but they seem to quickly
become unstitched.

Are there any press studs or some mechanical fastening of any kind that
might be suitable and that i could install without having to do sewing
please. Grateful for any advice. Thanks.