It was mentioned that the end wheel could be switched out for a flat lap. How much and what is the part number for the flat lap that works with the Pixie?

You can use these 4" diameter 1/4-20 discs. Search for: 10199_CFG & 11150_CFG Or here are the links: https://kingsleynorth.com/canvas-leather-polish-discs.html https://kingsleynorth.com/lapidary-equipment-supplies/diamond-wheels-belts-discs/diamond-pacific-nova-discs-4-inch.html