Think I've found your Peter Bush at FindAGrave.com Blue Ridge Cemetery, Roanoke Co., VA
P. Bushaged 78 years (pictured is old weathered stone, cannot read from photo, but if this IS Peter and he was born about 1763 and died in 1841 - this would appear to be same. Especially since also buried is an Alice Bush (nee Riveer) with no dates given. others in cemetery are: Columbus Fields Ashburn Bush 1892-1968 J R Bush Lula Waldron Bush1895-1957 Mary Bandy Bush d. 1893 T J Bush1852 -1853 Thomas Johnston Bush1797-1865(Your son Thos also born 1797) Thomas L. Bush1825-1888
I have info that a Peter Bush left a will in 1841 in Roanoke County. Can you access a transript??