Not to worry! This one has an easy and cheap solution.

You'll want to acquire either a defogging spray or Frog Spit (links below) and apply it to your window every so often (one application usually lasts me through a weekend).

With the sprays, you just do a light spritz on the inside of the window and lightly rub it around for even coverage. Let it dry.
For frog spit, apply a couple spread out drops to the inside of the window. Lift the cloth mesh if your window has it and then and tilt the window to roll the drops around for even coverage. Let it dry.

Afterwards, the more you touch your window, the sooner you will have to reapply the defogger.

If your suit has mesh over the window, this is to partially obscure your face. However, there IS mesh over the window of this photo and it doesn't obscure much from the outside. It won't be a problem if you want to cut off the mesh, and it may make applying defogger easier.

Adding a second fan to your suit will also reduce fogging somewhat.