There's usually at least one Sovtek head going on eBay a week.
Sovtek Mig 50 and 100. And some different variations, usually just knobs are slightly different.
The Mig 50 head is usualy around $125-$150
And the 100 runs about $200-$250
that's usually what I see on eBay with the Sovtek heads, though, sometimes people go mad and just want to win and sometimes they'll go for $325
I was suggested to check out the sovteks sometime ago, so I check eBay now and then. Haven't bought one or played through one. But I still might buy one someday.
I heard you can only find them at auction sites, or used at non-major chain music stores. So, don't bother checking guitar centers, or any big name music store.
As they aren't being made anymore those are the only two real options.
But check eBay, there's usually always one-three up there.