Old Bug, I don't know why I didn't think of it, I have a turtle No. 19 with a new 18 tooth gear for $50.00 plus $5.00 for shipping. Perhaps this will work for you. Elmer Swift twinjoan@gmail.com
Your can buy new 17 and 18 tooth gears and the correct turtles for those gears at Bratton's Antique Auto Parts located here in Maryland. The last time I checked they were at about $25.00 each. They have an online catalog.