Batteries are the part people replace when the fault is somewhere else, so we test before we sell.
Bring the machine or bring the battery. We put it on a tester and tell you what it is holding. Perhaps half the batteries brought in as dead are fine and the charging side is the problem, which is a repair rather than a purchase, and we would rather say so than sell a battery that dies again in a month.
We stock the common sealed battery sizes for automatics and the two most used car sizes. Anything else is ordered and takes about three weeks on the boat, and we say three weeks rather than a fortnight because the boat decides.
Bulbs, plugs, relays, starter solenoids, brake switches and handlebar switches are all on the shelf. Wiring looms and control units are not, and a shop that tells you it can get you a control unit for a fifteen year old machine in a week is a shop to be careful with.