Forgetting underpants isn’t that bad – you can wear cycling shorts all day and no-one’s the wiser. Although they aren’t the most comfy.
Shoes – no biggie if you are at your desk a lot.
Shirt – much worse. You look a tool in your cycling top and you stink to high heaven if it’s been a warm day.
Belt – very easy to get around – simply tie a bit of string through the first belt loop on either side. I once did a whole cycling holiday like this, but intead of string I used zipties. Problem was they were non-reusable, so urgent toilet stops were made all the more urgent by having to fumble with a knife to get them open.
I also broke my glasses on the same trip and used zipties to mend them too.