I have bought multiple melodicas through Amazon with no problems, including several Yamaha pianicas. Amazon has multiple vendors for the P-37D and other models. I’m assuming you’re in the US. I see the one you must be looking at, at $86.32 with free delivery for Prime members. The 2-5 months for delivery is highly unusual and would make me nervous, as this is a readily available melodica. I bought a P-37D recently for $99.99 from Japan (via eBay) with free delivery that took about two weeks. Japanese venders are conservative in eqstimating delivery time, which in my experience is 2-3 weeks though they say it will take a month or two. But they’re all over the map on delivery costs.
$86.32 is a fantastic price. If you’re not a Prime member, how much is delivery? The 2-5 months might just be due to shipment from Japan, in which case my guess is it won’t take anywhere near that long. The Japanese vendors are very efficient and package well. I personally would go for it. I’m a Prime member. Amazon sets high standards for their vendors and has a lot of clout in resolving any problems.
Great melodica, by the way.