I've just been riding my 'ped without the benefit of registration (yes, which I should probably look into now that theft season is upon us). Is this an option for you? How observant are the police around your area? Do you mind risking a ticket?
Being a the kind of girl who dislikes stupid rules and regulations, I sometimes choose to ignore certain laws. Not that registering your moped is stupid (rather the contrar) but if you're running into that much hassle and the police are sort of lax, I say forget the laws and ride anyway.