(Founder/VC here) if you are in an area where there are VCs who invest in the thing you are founding, tell them that you are a solo founder working on an idea for X, and you would like to work from an office if they have a space you could do that from for a week. Just during business hours. Be a great guest. Polite, clean, quiet, etc.

Second option is that if you are a founder and you have a law firm you are working with, particularly a large startup one they have literal palace offices which alwyas have space. Ask then for if you can work for a week from an office space. Same deal.