The only pollster I’m aware of who polled this question late in the race was Yougov. Here’s what it looked like at their final poll:
More crosstabs…
People who voted in the Dem. primaries:
Clinton 83%
Trump 9%
Stein 3%
Johnson 2%
People who voted in the GOP primaries:
Trump 82%
Clinton 8%
Johnson 5%
Stein 0%
People who supported Sanders in the primaries:
Clinton 68%
Trump 15%
Stein 7%
Johnson 4%
People who supported a Republican candidate other than Trump in the primaries:
Trump 70%
Clinton 11%
Johnson 9%
Stein 0%
97% of those who backed Clinton in the primary still back her in the GE. 97% of those who backed Trump in the primary still back him in the GE.
This is from a national poll taken Oct. 30 - Nov. 1, whose topline #s were:
Clinton 45%
Trump 42%
Johnson 4%
Stein 2%
Of course, that lumps Cruz voters together with Kasich and Rubio voters. Not sure how it would be different if you were just considering Cruz voters alone.
Also, of course, Clinton got a larger share of the vote in the Democratic primaries than Trump got in the Republican primaries. So he would have to win over a larger share of the Cruz/Kasich/Rubio voters than Clinton would have to win of the Sanders voters in order to keep pace with her.