Thank you for your clarification.
The lenders - in my opinions - tend to be fairly strict and will want to see proof of the money 30 days prior. Or rather, their underwriters will. So even if the lender waives it off saying "it's just a thing," the underwriter is much more likely to take it seriously.
I am afraid I do not have an immediate solution for you. You are essentially seeking extra capital but cannot spend what you have meanwhile until the mortgage is finalized. The best thing I can think of is possibly perhaps expanding your current credit card limit? If so, then the soft/hard pull by the card would normally only cost a few points - not enough in most cases to scare the lender prior to closing.
Please note: If I tell you simply what you wish to hear, this would be unfair to you. I need to be honest with you and sometimes this means providing information that is not optimal. Negative ratings are reserved for experts who are rude or for erroneous information. Please rate me on the quality of my information; do not punish me for my honesty.
I hope this helps and clarifies. Please use the SEND or REPLY button to keep chatting, or please RATE when finished. You may always ask follow ups at no charge after rating. Kindly rate my answer as one of TOP THREE FACES/STARS and then SUBMIT, as this is how experts get credit for our time. Rating my answer the bottom two faces/stars (or failing to submit the rating) does not give me credit and reflects poorly on me, even if my answer is correct. I work very hard to formulate an informative and honest answer for you; please reciprocate my good faith with a positive rating.