How you resolve it will depend much on the type of relationship you have with the other individual.
A possible way to approach it is to ask the person how much they are willing to spend. In other words, try to determine if their expectations are in line with the financial realities.
Many times people are familiar with something due to a former presence, yet have no idea how limited availability directly impacts cost.
Sometimes you may even have to get the other person involved in the material search.
This isn't knife related, but here's an example to show what I'm attempting to convey:
A lady called me up and asked if I could "fix" her nightstand. This was a gift that her father had made for her over forty years ago. After her husband recently passed away, she moved into one of those "retirement" apartments.
The movers had busted the apron on the nightstand, and one of the legs was split.
So I go over there to take a look, and immediately lose my breath when I see it. I nearly fell over right there!
The entire piece of furniture was constructed of solid Brazilian Rosewood! No veneer; it was the real deal.
My mind started racing. Where was I going to get that much of that type of wood?
So here's a nonverbatim rehash of the conversation:
Me: "I'm not too sure about this. This type of wood is going to be pretty hard to come by, and if we can even get it, it's gonna cost dearly."
Her: "Really? Now you sound like the guy I take my car to."
Me: "Do you know what type of wood this is?"
Her: "Of course. It's Brazilian Rosewood. Can you fix it or not?"
Me: "I don't want to fix it, but yes, it can be fixed. Fixing it isn't the problem. Getting the wood is, though."
Her: "I don't understand how that can be a problem. My father always had a bunch of this in his shop. When he got too old to work anymore, he sold everything off to a guy he taught."
Me: "And is this other guy still around? Do you think he still has any of it? If I buy this at today's prices, it's probably going to cost well over $200 for two little pieces of wood. That's if we can find it."
Her: "I'll call him right now."
So enough of the conversation.
To make a long story short, this lady's father had been a luthier, and he had been deceased for nearly thirty years. This was long before CITES was even thought of.
I knew very little about her father's trade, but apparently that type of wood was (and still is) highly coveted for its "musical" qualities. So with her growing up around it, the wood was sort of a regular occurrence to her.
She appreciated the beauty of the wood, but since she had never really taken an interest in any of her fathers doings (she was a retired math teacher!), she did not fully comprehend the situation as it applies to today's circumstances.
To her, the nightstand had always been an object of high sentimental value, not financial value.
Yes, the other guy still had some of the wood from her father, and I contacted a furniture maker to do the repair. Everyone ended up being happy, except for the moving company that had to pay for it all.
So you may be facing a similar situation here. Maybe your client has some sort of particular reason that she simply has to have that bog oak.
Most people appreciate the rare stuff, and that's usually why they want it. But in my scenario above, the lady didn't even have a clue!
If you can, try to get an idea why she wants it (without appearing too invasive, of course).
Maybe she will settle for a substitute, maybe not. But only then will you get a sense of direction for the project.
Good Luck,
Rob