The online community of knife collectors, A Knife Family Forged in Steel
Kevin .. I PM'd you a response ....................
A.G. Russell's "steel thumbnail".
Many of the major manuf make their own versions.
At one time or another, just about every manufacture has offered them so if you want a specific manufacture just keep looking for them to show up on ebay :)
Thank you, Steve. I bought one made by Case. Thanks.
Rough Rider makes a knife opener like you're looking for.