No, there isn’t a form available for this purpose. Past agency disclosure forms led to misuse and misunderstandings about the nature of those forms and their intended purpose. Don’t confuse this representation disclosure with the written notice about brokerage services.
Verbal or written disclosure of representation is acceptable, but it should be done upon first contact with another party to the transaction or with another licensee representing a party to the transaction. In this scenario, your call or email response will be the first contact with this prospective buyer.
If a contract is subsequently executed by your seller client and this prospective buyer, a written notation of who you represent will be provided in the Broker Information section of the TREC contracts.