If you cannot find a name that you love, pick a name that you (and your son) can live with. Something fairly ordinary, easy to spell and pronounce, and unlikely to provoke a strong reaction either way would probably be best. The good news is that I'd put all of the names you're considering in that category. As you can't use them, I'd branch out and start considering top 100 names like:
Matthew
Thomas
Peter
Oliver
Luke
Oscar
Leo
William
Joshua
George
James
Daniel
Jacob
Ethan
Samuel
Joseph
Noah
Benjmain
Henry
Isaac
Sebastian
Adam
Reuben
Gabriel
Arthur
Frederick
Stanley
If you're looking for a Scottish name, the obvious contenders are:
Alistair/Alasdair
Iain
Aidan
Rory
Callum
Fraser
Euan
Scott
Douglas
Bruce
Stuart/Stewart
Graeme/Graham
Erskine
Fergus
Hamish
But maybe you could also consider less traditional/common choices like Stirling, Boyd, Logan, Arran, Torquil, Brodie, Clark, Munro, Reid and Ross too.
It's hard to gauge what your style is but here are some 'classic Scottish'-type choices you could also think about using: Christopher, Clement, Francis, Gabriel, Hugo, Peter, Theodore, Rupert, Nathan, Nathaniel, Ralph, Robin.