[Easiest way to stretch a 1px column to fill an image?]

I'm trying to find an easy way to take a 1px selection from an image and stretch it the full width of the image. I tried using the column selection, copying to a new layer and stretching that layer. However, the stretch operation interpolates the pixels to transparent. Cool effect, but not what I'm looking for. In photoshop I would have just cmd-right-arrowed the selection until it filled up the image. Any easy way to pull that off in Affinity?

 

Thanks!