Following on from my weird sump plug thread. Or the whereabouts of a new one?

Tried your local motor discount shoppe? Failing that, Volvo will probably do you one for under a fiver. Did you get the old one out yet?

Alas, not yet.
Had to replace rear brake cylinder components last weekend.
It's going to be fooked when it comes out which is why i'm sourcing one before getting it out.

Same here, I bought a whole gearbox to get one.

1) Volvo dealer - usually helpful as they can look it up and give you a part number even if it's NLA.
2) Renault dealer - usually unhelpful, but the odd one is. Either you need to know what Renault it might have been fitted to otherwise they won't know where to start, or give them a Renault number to look up.
3) Aftermarket. Good motor factors will be able to get hold of the things.
4) Scrapyard. If you can find one with the car you want.

*IMS Verbindungstechnik PDF catalogue (1.29MB)* CLICKY LINK

Anything useful in there?

There's some info on thread sizes and depths and the pictures show the head types. Also has OEM numbers so useful for cross referring back to.
For instance there is a Volvo plug in there, which isn't too dissimilar to a Renault plug, but with a more tool friendly head.

Lastly, when attempting to remove plugs, use the right tool. Old Renault ones are 10mm square and a 3/8" drive will fit, but will wobble which isn't good for tight plugs. Either a Facom wrench with 8mm and 10mm squares can be bought, or Facom socket bits.