Hi Henry, are you sure the internals are a P37D? They used to fit Angel melodyhorns, one of the cheapest melodicas available. If it is a P37D, then that’s a step up. You can buy Yamaha reed plates directly from Yamaha, I’ve ordered many in the past. I’ve copied some info from a previous post at the ned of this message
Not sure about the hose lengths…
Orders for Yamaha Instrument spare parts can be obtained from the following locations:
For UK Customer’s: Yamaha UK Spares – 0844 811 1116 (Option 2) or via your local Yamaha Music Dealer.
For Republic Of Ireland Customer’s – Yamaha UK Spares – (0) 15262449 (Option 2) or via your local Yamaha Music Dealer.
The part information that you have requested is below.
W4110210 High section reed plate, no stock but available to order from Japan and the cost is £15.08 Inc of VAT
W4110310 Middle section reed plate, same information as above.
W4110110 Low section reed plate, same information as above.
Handling is £3.60 and you can order with a credit or debit card on the contact number shown above. They will take about 4 weeks to arrive from Japan from order.
The phone number in the U.S. is 888-892-6242 (option #1). I asked about reed plates for the P32D:
Part #’s..backordered 4-6 weeks from the time you order.
W4040221..low reed plate P32D..$24.28
W4040231..high reed plate P32D..$24.28
There appear to also be delivery charges, though probably not if you can order through a dealer with a Yamaha account.