MayDay can send you an emailed invoice at your request. Pass this on to firstname.lastname@example.org or a Money Spoke and ask the spokes to consider. Usually MACC Money can easily pay this invoice online. Be sure to follow up with macc money if you do not hear back in a day or two to ensure it is paid before the event.
You can money to MayDay via their venmo account (@Mayday-Space) and pass the hat at the meeting for reimbursement if you do not wish to involve the money spoke or if they decline your request for some reason.