Maybe I'm crazy but I do not get all the overly expensive suggestions for what is a $5 fix for a used 20+ y/o bike.

Buy a P clamp.

The OP'S says he wants to mount a front basket. This requires the most simple front rack available without lowriders. New, about $32CAD.

Really, replace the fork on a used mtb with carbon fiber because there isn't a fender eyelet to mount a basket...