I do not have an Oxford shell, but am pretty familiar with bailers.  There is no bailer listed in either the kit list or the accessories list for the OS so it is anybody's guess what the builder used.  If you post a picture, somebody may recognize the brand.  Otherwise, you are stuck trying to compare with catalog pictures.

Can you tell where the bailer is leaking?  If it is the bailer itself, they may sell replacement parts once you figure out the manufacturer.  If it is leaking around the perimeter of the bailer, then you will have to remove and rebed it.  If the builder did a good job of sealing the ply with epoxy and used a removable sealant like 4200, this will be an easy job.  If they used a permanent sealant like 5200 or epoxy, it will be much harder.  Before you rebed, make sure that the plywood edge is sealed well with epoxy.  If the end grain is not well sealed, water will wick into the ply and cause stains or worse.  Hope that this helps.

   Outstanding information, thanks.  It’s an Anderson mini from what I can tell...