Hi basso,
You could find out from your local lawn bowling club the name of the firm that sharpens their greens mowers and contact them for a price on a 17" reel......depending on the condition of the bottom blade (you may need a new one) and they can supply one for you(not too expensive at roughly $30) I pay $70.00 for a sharpen. Once done, they cut beautifully.
Regarding the Model No's, mine is a Model 450520. I don't know if there are differences between the models, but from the parts side, they are all the same....known as the Model 45.
Try eBay....search term: "Scott Bonnar" as see what pops up.
Good hunting,
