Unable to calculate profits - need advice

Hello there, So I've been buying goods in bulk/joblots to sell individually from eBay. The problem I'm having is that I am unable to calculate accurate profits made due eBay removing purchase history information such as (imagery and descriptions). What advice or how to tell hmrc, that I cannot provide accurate profit information.

Hi,
Self employed individuals are responsible for keeping their own detailed records of all sales transactions, to enable them to declare accurate details of income and expenditure:
Business records if you're self-employed
Thank you