Are there various websites/services that allow you to submit your brokerage statements as a verified track record?
This kind of a service is called an "audit". It costs money and time. Unless a track record is audited, just posted to a website somewhere doesn't exactly make it special.
... um... you need an accounting firm rather than a website. Certainly, E&Y, PriceWaterhouseCooper and the likes all have auditing arms. I suspect there are plenty of middle-market firms with certified auditors who can do the same. Are you sure you need to audit your returns... there are very very very few cases where this is necessary.