Regarding spares, new is always prohibitively expensive for hobbyists anyway - so even if you could buy new I'm not sure it's recommended!
I still haven't sorted out coins for my MFME cab plan yet. But I'm going the single hopper route - it'll only pay out one denomination of coins.
That's no good for older machines, which typically pay multiple denominations (say 20p, or 20p token, as well as £1). Or some seaside machines which might have a 10p hopper alongside a £1 hopper to pay smaller wins
Hence why I assume people run dual hoppers