Here’s a good one ported from libretto, originally written by Timothy Lottes: https://github.com/Jjagg/mg-crt/blob/81bcf73e02f1087a6223b14aa97145478ead45fd/Game1/Content/crt-lottes-mg.fx
If you look through the commits you’ll see specific optimizations that may or may not suit your purpose. The biggest win by far is to use 2 for the gamma exponent instead of 2.2. I tried all libretro CRT shaders and thought this was the best one.
Here’s the repo with libretro shaders: https://github.com/libretro/common-shaders
They’re pretty easy to port to HLSL for MG. I recommend trying out the effects with a game to see which ones you like 
I recall writing a script to automate porting over the shaders for MG, if you (or anyone else) is interested in it I’ll look around if I can find it.