Letter to Predecessor CPA

I have a very small CPA practice.  I have been approached by a potential client to handle bookkeeping and tax return preparation.  He has been with the same people for many years  (a husband/wife team - husband is an EA and wife is a bookkeeper).    Does anyone have a proforma letter or sample they can share with me to request records and files from a predecessor?  Any help would be appreciated.  For some reason I'm struggling with crafting my request.  Thank you!