Without researching it I believe you could. 1) You have a no-cost option available. 2) Disclose it and 3) I would make the fee reasonable.
Since there is a free option available, assuming it can handle the traffic you anticipate, you needn't worry about a "chilling effect" this fee would have on the consumer's rights to get this information.
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AndyZ CRCM
My opinions are not necessarily my employers.
R+R-R=R+R
Rules and Regs minus Relationships equals Resentment and Rebellion. John Maxwell