110V sewing machine plugged into 220V - DIAC blew?
The component is almost certainly a metal oxide varister. It is designed to absorb voltage surges by shorting them out but it is not designed to take sustained overvoltage. Connecting a MOV chosen for a 120V only application to a 240V supply will almost certainly destroy it. 

As to replacing it unfortunately googling the part number printed on the device turned up a blank.

http://www.littelfuse.com/~/media/electronics_technical/application_notes/varistors/littelfuse_selecting_a_littelfuse_varistor_application_note.pdf suggests that for 120V applications you want a MOV with a continuous AC rating of about 140V (to allow for supply voltage tolerances). 

Selecting the peak current rating is trickier, personally for a one-off repair I would just go for the highest peak current rating I could get in an acceptable package size.