There are 2 Harristowns in Kildare in the area of Portarlington. I believe that the Watsons were living at Harristown Lower (12 miles from Portarlington, and not Harristown 24 miles from Portarlington)
The Harristown we are after is in Parish of Monasterevan, which in addition to the district of Monasterevan proper, the present parish includes the old parochial districts of Kildangan, Nurney, Duneany, Harristown, Walterstown, Ballybracken, Lackagh, and part of Lea, all which,-except the townland of Inchacooly, in the Queen’s County,-are in the county of Kildare. A considerable portion of this district formerly belonged to the barony of Upper Philipstown and King’s County, but was, by the Act 6 and 7 William IV., incorporated with the county of Kildare.
The Sextons (one married an Elizabeth Watson) are in Griffiths under Harristown Lower, Harristiown Parish, Kildare. And in fact the only Sextons in Co Kildare in Griffiths are in this Harristown.
1809 Game Licence issued to WATSON Thomas Baltracy, Kildare (2 miles se of Naas)