You’ve got a few choices:
1. Be your own agent. You’ll need to be up on legalese and contract-speak, advances and rights, so think carefully whether you want to spent a lot of your energy on this side of the business.
2. Keep looking for an agent in a Pollyanna’ish attack of optimism. Don’t despair – the right agent may just come along or have room freed up on their books!
3. Use a publishing advice service – this kind of organisation will look over your contracts, explain them, suggest amendments, etc, and give you advice about which rights to sell and which ones to hang onto – Alex Adsett Publishing Services is a really good place to start.