The serial number formats used for acoustics are numerous, and I haven't yet really tackled the task of trying to document them. I would guess that you're right that your bass was made in April 2001.

To find parts, your best resource is Hoshino's parts database.

Pop in your model number in that site and it will provide a full parts list (provided it was made since 2000).

However, in this case, it's not going to do you that much good, since the particular saddle (part #5ASD08D) used on these has been discontinued. A quick internet search doesn't turn up any sources, but you might be able to find one floating around on eBay or somewhere.

But realistically, even if I could find the OEM part, I'd opt for just replacing that stock saddle with either one cut from bone or a GraphTech TUSQ saddle. Any decent luthier should be able to get you set up.