We need to distinguish between two categories of Sanders-Trump voters. First are those represented best by primary voters in Oklahoma or West Virginia: once again they voted against Obama by proxy and would vote Republican in GE anyway. The others are those Hillary did not manage to convince in GE. Given the fact many deep red states Sanders won had caucuses, there are not that many of them, actually.
-How about those in Arkansas? It's a fully open primary, unlike WV and OK, and it's a fact that in quite a few Arkansas counties, despite HRC winning the Dem primary in a landslide in 2016, there were more Dem primary votes in some counties in 2016 than there were HRC general election votes.
Also, there were a number of these in Michigan, and probably WI and Indiana -all states O won in 08.