Thanks for your reply. I investigated a few potential sources and came up dry. As was mentioned, the few sets that are showing up on eBay are priced incredibly high....often 2 1/2 times what they could be bought at StewMac for a while back.
Ordering from Gibson probably isn't an option for me. My tuners are on one of my partscasters, a Bigsby Stratocaster, so I don't have a Gibson serial number to provide them with.
I got lucky and just found a guy on eBay with a couple of single tuners at a real world price. They're gold, but I'd much rather have one gold Steinberger on a guitar with black hardware than a set of inferior all-black replacement tuners.
I bought one of the tuners on eBay, and probably would have bought the other for a spare, but money's tight since I only retired a month ago. If anybody else is interested in the last one, the eBay item number's 252448612150 and it's 28.00 USD.
Thanks again for your help.