2 years since I've purchased the TCE gigbag for the Rebel Head and I haven't got any complaints.
It keeps my RH450 safe. Even when the bag has fallen to the floor.
Also the zips keeps working fine after 2 years.
Based in my experience, I highly reccomend the TCE bag If you have to carry on your RH frequently to the rehearsals and gigs.
For the knobs replacement, you could put in touch directly with TCE, perhaps they can help.
#48 Gibson Grabber/Ripper/G-3 club #TC RH450 Club
#412 Musicman Stingray Club