Yeah ebay and they mostly come from China dirt cheap. if you buy from a US source for much more you are probably getting shafted as they would have got theirs from China dirt cheap. Don't forget to get a replacement relay so you don't have to use resistors to correct flashing speed and make it work. Read similar threads here on forums.
A common problem is LED requires specific =ve and + wiring where as 12v incandescent just needs a current. A lot of blinkers/indicators have been cross wired at Triumph factory during build and still work but may not when using LED versions, simply swap around wires to terminals and voila the LEDs work.