We find the "Rochester Medical" has the best Catheters. A lot of the ones, especially "Freedom" are awful. Here's the link if you want to try them out.
Medium 29 mm condom for p-valve
Or as I like to call that size "Extra Medium"
Don't forget to always keep an extra condom with you... in the 44mm size. This way when another diver says says "Damn, I forgot one," you can say "No sweat, I've got an extra..." and toss one their way.
The look on their face when they come out of the head after "trying it on" is always priceless!