A loader on a YM1900 is typical of a very specific section of this market, which I will hence forth refer to only as a "very specific section of this market" lest it's defenders come out in force to lambast me---again. IF that is the case, it is likely going to be either a non-branded loader or a bulldog, and the only OEM parts (if there are even OEM parts to be had) will come from a dealer in this "very specific section of this market". That said, unless they are using completely bastard parts, one should be able to get most, perhaps all, of the necessary parts to repair cylinders from a good hydraulic supply source. None of this will substitute for someone with the knowledge to make a good diagnosis, so if you don't understand how the loader works, you probably need to 1. take it back to the seller, 2. find a dealer willing to work on it and take it there, 3. find a good independent mechanic to look at it for you.
I know you don't want to hear this, but I would not invest a great deal of money, as the 1900 is a model older than most sold in this market, and not highly regarded...it's resale in the market among those familiar with Yanmar is poor. The upside is that there are enough parts out there for it to allow one to keep one going if you are already invested. (we can get most engine--piston/head gasket/etc-- and component--starter/alternator--parts)