The only documentation I have personally seen on Isaac Van Sickle is a transcribed copy of the Orders In Council from 14 December 1816, which says,
"Humbly sheweth that your Excellency's petitioner resided in Morris County in the State of Jersey in America before the breaking out of the Rebellion, that he joined the Royal Standard in the year 1775 and served his Majesty as a private in the Jersey Volunteers commanded by General Skinner until the end of the same - that he came to this Province in the year 1797 where he has since resided. Wherefore your Excellency's petitioner most humbly prays that your excellency may be pleased to order his name to be inserted on the UE list.
Isaac X Vansickle
Ancaster 5th July 1811
A copy of this document (or a transcribed copy) can be obtained through the Ontario Archives and the Untied Empire Loyalists' Association of Canada.
And though I do not know exactly what they house, I do know that the Ontario Genealogical Society, Hamilton Branch, has several records on Isaac Van Sickle.