Hi Jeremy,
The SYL-212 is still being manufactured by Sylvania Europe - but not easy to find today! In USA market it is better known as a type CYN, CFC or A1/212 and you may find it under those names in some special photo lamp distributors.
If you get nowhere, contact the Sylvania HQ at the address below and I am sure they could put you in touch with a wholesaler who recently stocked up on lamps of this type.
Sylvania Special Products Group
Industriepark 13,
Soldatenplein Z2,
B-3300 Tienen,
Belgium.