I have an HH300, its around a 2001 model. It still runs good but I would like to test the nitrogen charge but I can't seem to find a test/refill kit that matches it fill port. There is many kits available online but seem to be a different style. The manual just says charging kit. The valve has a t handle to open a needle valve in the fitting on the breaker. I'm curious if anyone know where to get kits that fit older breakers.