Biked across town to talk to W8TAM who gave some good advice on attaching an antenna to my bike rack. The suggestion was for an NMO mount which would easily handle 2 meters radio and could be adapted with a different antenna to also support HF. When not in use the antenna could detach, and I could still carry groceries with it attached.
This is the recommended mount for my application, from Breedlove:
I need to measure to make sure everything will fit on the bike!
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