It may be worth trying the local motor factors or even ECP.
For my 205 no one stocked the fuel pump relay online, but I got one from the motor factors for £20.
Sister's Saab was the same. Bar Big Redd and other brake companies, I couldn't commonly find the slider kits easily from motor factors. I walked into ECP the other day and got them straight away for less than what the other folks charge .
The top cover on the relay looks like it's just held on with a "barb" at each corner, I'd be tempted to open up the failed unit - if you can find a dirty contact or loose wire fix it and keep it as a spare