Finding a similar setting is gonna be hard. I can't really think of any. The only other setting with the usual high fantasy creatures in a sort of modern world I can think of is Shadowrun and that's cyberpunk, not steampunk. :-/
However, the game was design-wise sort of similar to Tim Cain's previous game Fallout (1), though you should have heard of that game. Fallout 2 has more stuff to do but also has a bit more inconsistent tone.
If you have tough enough skin for it, you could try asking on rpgcodex.net, though you'll probably be trolled a lot.
They also usually mention Arcanum and Fallout along with Planescape: Torment as the holy trinity, so you might wanna check out that game too. It has a very cool setting too. Those three are pretty much the best RPGs of the late 90s (if not all time).