Oli, wazd is going to make your layout into a vector file for you, "that's part of the deal". I don't know if you're already in contact with him? He's been away for some time, but he's back

I went to a local (Eindhoven) engraving/3d-printing/custom t-shirt shop and they said they need a file (most vector files will do, but even a high res jpeg could work). They prefer a file where the corners are physical reference points so they can align their engraving machine from where to where it should engrave the file onto the keyboard. So no file with whitespace aound the layout, the left top of the file should align with the left top of the left top key.

I expect wazd to make me a vector file and I'll just walk to the shop with my keyboard and the file.

With some luck I'll be able to have my keyboard engraved this week. I'll post pictures.