Most mental health facilities will have the forms for powers of attorney for healthcare on hand. If you are visiting your spouse there, ask the patient representative or someone staffing
If this is not convenient or your request falls on deaf ears for some reason, you might try downloading the form specific to your state from the U.S. Living Will Registry website, which contains state links.
State laws differ as to what it takes to finalize such advance directives as to signing, notarizing or witnessing. But all of them require that the person making it must be legally competent--that is, able to understand what the document means, what it contains and how it works. Depending on his current condition, that may or may not compromise your spouse's ability to make the document final.
However, if you are seeking a power of attorney for finances that would take effect immediately and allow a person to take over financial matters for your spouse, then you can be fairly confident in using a prepackaged form or software program to get the document.
A few words to the wise: When searching for a self-help product that offers a power of attorney form, make certain that it is state-specific and comes with good instructions, as state laws differ on what may be included and also on what formalities you must follow to finalize the document.
the department of social services for the forms used you seek. The friendlier types may even help provide advice for completing them if you get stuck along the way.