I have a realistic assessment of who will want to work with a 40-year-old first time novelist, but I found an experienced senior agent whose interests map well onto my manuscript (science-heavy coming of age romance in a foreign country). I feel too humble to think she will want to deal with me, but I sure would like to know if she has a recommendation for someone less busy who might have more time to invest in a rookie.
Should I include this sentence: I understand that you have a large book of existing clients. If you have to pass, I would greatly appreciate any suggestion you might have for an agent who may be more actively looking for new books.
Or does that sound amateurish/nuts?
First of all, and let me say this as plainly as I can while striking you on the head with a cluestick: you do NOT have a "realistic assessment" of anything here. Nor could you. You've probably never been inside an agent's office, let alone worked with one. Repeat after me: "I am clueless."
Then say this: "I will never ever ever again assume that I am less than exactly what an "experienced senior agent is looking for." Repeat as often as needed.
I see this in women more than men, and too often in writers of all genders: some sort of assumption that you are asking for a favor by querying your manuscript. You're not. You're offering your work for representation in what we both hope will be a mutually fulfilling endeavor. Often that turns out not to be the case but it's the starting point for every query. Don't assume failure. Don't assume you're not worthy. BE FUCKING WORTHY (ie be prepared.)
Oh, and as to your question: don't ask for a referral. If any agent offers one, you say thanks and act on it immediately but don't ask. Agents are actually the worst people to ask since most often you know more about what agents are looking for than her friends do.
Now, put the clue stick away and get back to querying.