First, make sure to verify if your fire extinguisher can be refilled or recharged. If a metal valve is located where the nozzle connects to the tank, it can most likely be refilled. If the valve is plastic you’ll probably have to get it replaced.
Your local fire station may have a refilling program. Be sure to give them a call. If they can’t do it, they’ll know a few vendors that may be able to help. An ABC type fire extinguisher can often be refilled for $20-$30.