Yep, the range of aftermarket parts is limited, right enough.
To add to SuperDooper's list: blades/bolts, drive chains and small sprockets, and wheel drive clutch cork linings are available through at least one alternative wholesaler [GA Spares]. Their website is useful for cross-referencing Greenfield part numbers with standard industrial designations.
Belts and bearings, and steering rod ends, tend to be standard industrial types on Greenfields.
