Think this is quite common my 5th to reverse syncro is slowly on it's way out but not had a chance to source new box but new oil dose help make it last that little longer
i know the sync rings r about 30 quid , replaced 3rd and 4th gear sliders and sync rings last year for the sliders and sync rings it all cost about 260 quid from Mitsubishi.....just for the 2nd gear from them its 179 + vat + slider and sync rings not cheap.....