URGENT: Solicitor/Accountant Letter for Swiss Schengen Visa

I need a letter from an accountant/solicitor to prove I'm self-employed for my Schengen visa appointment. I need this by 10 am at the latest uk time - 20th August 2024. I have the template letter ready - it just needs to be put onto an official letterhead. I can provide whatever information is needed to verify the details in the letter.

Please find below what it states on the visa supporting documents section:

Self-employed: Letter from accountant, banker or solicitor (dated, not more than
one week old) including:
- Original wet signature (it must be clearly stated if the letter cannot be signed by
hand)
- Name and address of applicant
- Nature of self-employment or business ownership in the UK
- Bank account statement for the past 3 months
- Position of signatory
- Self-assessment form edited by HM Revenue & Customs