of course he should be the one to purchase your new visors and mats.
unfortunately. honesty and dealerships don't mix. I know you say you don't have the cash right now. but I think the only way for you to get reimbersed would be for you to buy them and then hand in a copy
of the receipts.
didn't you mention he was a consignment dealer. their lower than regular dealerships.
have him sign a receipt of getting said copies. if he says he wants the originals
tell him he willget them when you get reimbused.
return them for the money and remove the other vent visors.
second and more important, didnt he say he could sell your car for what you wer'e asking for?
He should be responsible for the difference. due to him putting on the extra miles.