BB, we glider pilots use external catheters, a bit of tubing and bags or bottles. Saves fumbling in the cockpit.
I like these:
https://www.urodry.com/products/geewhiz.html
There's a wide variety available. Stay away from the ones with adhesive (think ripping off a bandage) and and the flimsy ones.
For more info, search "glider pilot relief".