Hi Alette,
Thanks for reaching out.
There is a bike hire located on Inis Meain by the old pier on the Island which is about a 40-minute walk from the new pier. In summer months they may be available from the new pier but out of season, it is recommended that you reserve them ahead, or bring your own. You can find out more
here. I would recommend contacting the ferry company just to confirm this, and explain you are looking to rent a bike, as the other two islands are the main hubs for bike hire.
Let me know if you have any other questions and I would be happy to help.
Many thanks,
Cathaoir