An overlocker bulb

We recently had my mum and dad (Steveng) over (they went to the school music celebration while I was at work). Mum mentioned she'd bought a new sewing machine bulb but it only came in a pack of two. Today I finally remembered to check whether the spare one will fit my overlocker - this one works but is fairly dim, very yellow and gets enormously hot if I'm using for any length of time so a nice modern halogen would be a treat! Unfortunately this one is the wrong fitting so I'll have to buy myself one rather than scrounge off the parents!