i bought some of those for about $1.50 each at a medical supply store in the NE (next to sunridge mall). I didn't bother getting extra blades, as it's quite risky you could slice yourself up trying to change the blades unless u have a special tool (at least that's what the lady there told me). at $1.50 each, I didn't care really.
Oh, and I bought a pair of 10" stainless steel foreceps (huge tweezers) for $5. now THOSE are extremely handy. One of my most used tools for the fish tank now
