Hi,
Stretchy trousers for when you have the catheter in place, eg. Brasher trousers from Millets.
Tena pads, level 2 certainly, even level 3. L3s get heavy as they fill though I found. Packs of 120 from Amazon or other suppliers.
Boxer briefs accomodate the pads well, eg Danish Endurance I have found.
P.