What crypto random generator C code could use on WP8.1?

I've taken some C code and compiled it inside a C++ WinRT Component for Universal Apps. I then wrote a C++ wrapper class to expose the functionality of C code to my C# Universal Store Project as per the manuals: 1, 2.

Works fine for Windows 8.1 part of the project, but fails to load the component on Windows Phone 8.1 saying just "The specified module could not be found". I've found out that the problem is that the C code uses the following random generator function:

# define RtlGenRandom SystemFunction036
BOOLEAN NTAPI RtlGenRandom(PVOID RandomBuffer, ULONG RandomBufferLength);
# pragma comment(lib, "advapi32.lib")

Which seems to be unavailable on WP8.1.

This MSDN page suggests that we should use CryptGenRandom instead, but the latter resides in Wincrypt.h, which is not available on WP8.1.

So, what random generator can we use from C code?