Hello, if you want to find a solution easily, it is best recommended to contact Mendix directly and ask if they can help. They will then use there partner network to help find a solution.
Alternatively, I would recommend NOT to re-instate the application, but rebuild it in a new mendix version. The amount of changes/improvements that the mendix software has undergone in recent years will make it more cost-effective to create a new application, using the lessons learned to improve on what has been build, than to re-instate the old application.
On sight developers are handy, but there are partners that can help you get underway with your project AND support your company by tutoring an employee to become a mendix developer.
with kind regards
Mendix Business Consultant at Bizzomate