If you what the cheapest solutiin look what bearings you have and compare them with other bearings from yamaha motocross/enduro models. One here on xt660 mounted a KLX650c front USD fork almost bolt on, read that or take the nearest USD you can find and let a workshop fix you stem to fit the other forks clamps.
I mounted a WP fork on my XT and you can read it under suspension. Now I own a TT600RE and had also change that fork to a WP USD.
