I have a 500 mL bottle of storage solution and I've cut a hole in the cap so that I can insert the probe. That is where my pH probe resides when not in use.
You can use the probe condom. However, you need to have a little dose of storage solution in there. The objective is to have a saturated solution of KCl in contact with the exterior of the bulb to help equalize the osmotic stress and prevent any water or ionic loss from the bulb.