Did you try selling it back to the garage you bought it from ? Or maybe try Delaney's in Harolds X ? And there's one or two scooter shops in Inchicore and off Cork St. if you check the goldenpages.
About 12-18 months ago the market really dropped for scooters, the insurance prices shot up to €1500/2000 for young people on scooters, and for some reason scooters don't seem to be that popular for over-30s. I tried selling my 8 month-old bike worth €2K back to the garage I bought it from & they'd only give me 800, and they really didn't want to buy it coz they didn't think they'd be able to sell it. In the end I kept it.