Mudguard? Mr. Mike assumed correctly that to be GB-ish for 'fender'?
What's the 'dated' part? Are you looking for the 'MX' look without a taillight? Those are a common replacement choice.
As far as 'with modification'..I think
any fender may well require that. The last rear fender I put on was an OEM Kaw KDX fender. I bought it specifically 'cuz I didn't want to mess with something that didn't fit.
Had to fuss with it anyway. I asked a couple of guys that had replaced more fenders than I ever will and their point of view was, 'They're all like that.'
I eventually gave up trying to get the OEM fender holes to match up to the frame holes..redrilled, reshaped, elongated whatever had to be done as was required.
I imagine it's the life of a dirtbike to have things like subframes (what the rear fender generally mounts to) tweaked to the point that plastics fit is problematic.
Good luck with yours!
**edit**
Click
HERE..a recent post regarding 'mudguards'..what fits what.