I have been like you using cleaned original 1" wicks.
Have you tried ordering wicks from Miles Stairs Wick shop? I was told awhile back that the wicks he sells are better quality and a thicker weave than others sold elsewhere by someone who was having a problem with finding wicks that fit properly also.
He sells three packs of 1" wicks for $3.45 and he says they are for old time lamps and greenhouse heaters, early 1900's Dietz Blizzard and Royal hot blast lanterns. It sound like it's worth a shot to me. Here's the link to his flat wick page on his site.