Alternatives for housing gaurantor

Hello,
I am a student doing PhD in France. I have been staying with my husband who is also a PhD student in an accommodation for students. we want to rent an apartment outside and unfortunately we need to provide a guarantor for this and we are unable to find an alternative. We are salaried (PhD work contract) but unfortunately both of us have croosed 29 years of age which means that we can not avail the 'Locapass' option.

Are there other alternative besides 'Locapass' and to avail those what are the requirements and formalities. Please reply as early as possible and if you have any website which has information in English please let me know.

regards,
M U