The GVB catalogue offers you a wide choice of electrophysiology articles for a very good price/quality ratio:

EEG:

• Electrocap headcaps
• Ergonomic MultiCap headcaps
• Bridge electrodes
• Cables
• Gels, abrasive, adhesive and conductive pastes, collodion

EMG:

• Stimulating electrodes
• Recording electrodes
• Ground electrodes 

Sleep:

• Piezo sensors
• Disposable sensors