There is a user group on Yahoo! called Bolensdieselgroup. Several Bolens part suppliers follow that forum. If you want to buy new parts, Rainbow Distributors in Honolulu has been able to get any part I've needed. They are a bit pricy, though
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Some of the parts on the G152 are available from dealers who stock Massey Ferguson. Iseki manufactured the G152 for Bolens and a similar model for MF in the mid to late eighties.
I hope that helps!