George, I have had a permanent suprapubic catheter for over six years and understand your dad's situation. I also wear my bag across the knee. I have the same issue trying to find and suitable trousers, I do wear smart jogger type trousers nearly all of the time, I also have the issue of the waistband across the SPC site. I have searched the high street stores for more roomy trouser legs without being to big around the bum and waist, I think the only option may be made to measure trousers. I would be interested to know what the sports trousers were you mentioned.
I found the bag on the lower leg was always falling down unless the strap was quite tight, post op for a couple of weeks is okay but long term when more active needs a different approach.
I use the statlock adhesive fixation device to secure the catheter. I do have a flipflo and short tube bag in a leg sleeve with one bag strap at the top, this help stop the bag sliding down below the knee. Another useful device is a lock for the leg bag tap, it saves accidentally opening the leg bag tap and getting a shoe full of urine. I use Bard bags and a bard uriloc, I rang Bard and they said they would send me a hand full ,must have small hands I got one. The uriloc may be a struggle if he doesn't have nimble fingers.
As mentioned I also use the bard urisleeve, it saves having to have two leg bag straps. At night I attach the night bag tube to my ankle with a thigh/G strap, it save any pulling on the night bag tube/leg bag outlet connection. I put my night bag on half a night bag stand that sits in a flex bag, not as big as a bucket and not as low as a bowl. I have had one night bag leak in over six years.
Hope all goes well for Dad.
Please let me know if you find any suitable trousers for him.
Thanks Chris