If all else fails there should be companies to recondition steering racks out there.Galahad submitted a new listing:
Wanted: 2007 Fiat Panda Steering Rack - Wanted: 2007 Fiat Panda Steering Rack
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In the old days pre electronic steering, the parts that wore were the inner track rod arm swivel which could be replaced, the bush in the end furthest from the steering wheel and if the play was at the rack and pinion area there were shims behind the plate at the bottom which could take slack out between the two gears.
Obviously the work should be done by a competent motor engineer.