I got my seal from EuroCarParts (via CP4L) very cheaply with discounts along with a sachs clutch and LUK DMS flywheel and all new bolts etc under £450.
It is an Elring seal marked 997.101.212.01 which was the latest part number at the time.
I borrowed a homemade tool from a member on here to draw it in evenly to the correct depth.
As above if you find its not leaking when you remove the flywheel, some say its best to leave it be.
Mine was weeping a little from the RMS but mainly from the IMS bearing cover which I re sealed after locking cams with a homemade tool and removing chain tensioners (which also got new seals).
Unless its actually dripping oil from the gearbox/engine join I wouldn't bother investigating, I was in for a clutch change anyway.