I don't have an AUS, but we were told not to cycle during RT due to exacerbating inflamation, and I bought this so I could continue cycling. I've continued using it months after treatment, although probably not necessary for a while, but not sufficiently uncomfortable (once you've got used to it and got it positioned well, which takes a few rides) for me to be bothered to put the original saddle back on.
VGEBY1 Bicycle Seat Saddle
I believe you can have the AUS above or below the pelvic floor muscle, subject to sufficient space. Might be worth asking the urologist which might be best given you are a cyclist.