Nice one still s8tannorm!
Not sure what kind of floats you have in mind, but http://flyweightdesigns do an ultralight packraft. Not certain what a bike would be like on that.
Sevylor do standard cheep dinghys, there was one design (can’t remember the model) that people used as a cheap packraft. The main problem with them apparently was the emergency deflate “feature”, whereby a tie down would rip off the hull mid float, deflating the raft in seconds.
The good thing with the Alpacka ones is they are fairly bombproof. I have had mine in 4 foot surf, and grade 3 / 4 whitewater, and it has never skipped a beat. They are expensive yes, but if you can reach to it, worth it.
Just uploading a video of my trip…