Here is the rather gllomy news from Tax Fix regarding obtaining duplicate P60s"
'Getting a copy of your P60
If you have lost your P60, you should first approach your employer to ask them if they can provide you with a copy.
Employers are obliged to keep records of pay for three years and so they should be able to provide you with a copy of your P60 for the last three years. The P60 will be clearly marked as ‘duplicate’.
HM Revenue and Customs (HMRC) cannot provide a duplicate of your P60.
If you need a copy of your P60 from more than three years ago, it is unlikely that you will be able to get one. Your employer may be able to provide you with a ‘statement of earnings’ on company headed paper which should act as a replacement for a P60.
Alternatively, you should contact your Tax Office. Your tax office will be able to provide you with alternative, official information regarding the amount of tax that you paid'
You could try the DWP, they may be able to assist.