or try someone like RS Components or similar..or google the manufacturer of the switch /button (telemeqanique ??.. if a top quality one) & find a local distributor... Some switches come in several parts & so you may be lucky & just buy the part that's failed instead of the whole switch assembly. If so you could find the part number then you might find the part on ebay.
(I'll assume you've looked inside the enclosure to see what is wrong & that it's not just a loose / burnt connection or some other issue)