How to make an IR proximity sensor work in daylight?
I suggest you try (you might need a combination):


use an IR remote control receiver (for a start, a TSOP) with an appropriately modulated source (36 kHz + 1 kHz). this will likely be the biggest win.
put the receiver at the end of a (black) tube, so your sensor 'sees' only the (reflected) light source
putting the source in a similar tube might give a little added benefit because it avoids reflection of the sunlight on your source