Walk behind Cub Cadet self propelled

[goat roper]

I have a cub cadet self propelled mower model# 12a-977a100, not sure how old it is. It has the Kawasaki engine with the plastic pull rope. The spring broke for the rewind, no replacement for the spring only available, you have to buy the whole top part that will bolt to the top of the engine - $38.00-$44.00. has anyone ran into this and fixed it by any other means. It looks very similar to one used on the old 6hp tecumseh engines, that sears had on their self propelled mowers a few years ago. Any help would be appreciated.
Thanks,
GM