Get a fitting from where ever you got your accumulators. It's probably a European fitting and most compressed gas shops won't have one. Then just go to any compressed gas shop to have them charged. Better yet, purchase a nitrogen cylinder and some fittings and charge them yourself whenever needed.
Sounds like (whereever you are) it's starting to get cold. Accumulators should be adjusted 2 or 4 times a years when the weather changes. The pressure drop from the cold weather combined with thickening fluid is causing your car to ride rough. You'll need to lose about 25 - 75 psig in them (depending oon the car) for the winter then raise the pressure in them again in the spring. I just adjusted mine about 3 weeks ago and do it every 3 months.