JiK
Our local knapper is quite fond of using empty champagne bottles as a source of glass for knapping. It's thicker than most plate glass and thus easier to control.

Giok
Any knapper (even me, and I'm no great shakes) can resharpen almost any stone (or glass) implement by reshaping the edge with some pressure flaking. The "retouch" is the main diagnostic feature that tells an archaeologist that the shape of the putative "implement" has been made as a tool rather than been made by accident, such as "grader flakes". And you can make one for yourself anywhere in the bush that you can find nice pits of rock.

But they don't have the nice built-on handles of your Skarsten Scrapers, agreed.

Cheers, Rowan