Here is a link to a site where you can see the SJA 102, etc.
http://www.velobase.com/
Both pictures were taken by myself. The one with the silver-toned name plate was purchased at Velo-Orange for $45 back in 2007 to replace the original derailleur from my 1977 Peugeot PX-10LE (a Simplex LJA 200 Criterium with cracked clamp hinge). The one with the gold-toned name plate was subsequently found in an old bike shop, and is currently serving on the PX, since the color matched the original rear derailleur. The silver one, no longer needed, was auctioned on eBay in very good used condition in June of 2008 and won by a notable CR List member.
I don't think this series is particularly rare; from what I've seen they don't command the kind of prices that the Super LJ's do, but I think they work well and look good, and so would be a bargain at $30 or $40. Hopefully, one will pop up for you on eBay.
Regards,
John Hurley
Austin, Texas, USA