Implementing a seedable CSPRNG in Visual Studio 2015 (VB.net)

I have looked for, and cannot find, any decent means of implementing a seedable Cryptographically Secure Pseudo-Random Number Generator (CSPRNG) for VB.Net. Anybody with cryptography/programming/VB experience knows Rnd() is crypto-suicide. Also, it looks like RNGCryptoServiceProvider does not (practically) allow seeding (From SO: no cryptography random generator seed allowed in C#?).

So, realistically, if I'm building a VB.Net Windows Forms application (Visual Studio 2015), how on earth do I implement a seedable CSPRNG where a password hash could be used as the seed? Is there a common library or something that people use? Or is it truly just kinda "fend-for-yourself?"