Custom Equipment - Revise C++ Software

We have some custom built test equipment in-house. There are limits defined by the code which prevents certain test scenario's that we need to change. The code is written in C++, and the changes are very straight forward. However, we do not have access to a compiler so cannot implement the changes ourselves. The company that programmed it originally are no longer available to us. We require someone who has the expertise to help us out asap as it is having a major impact on internal projects. On-site visit required to access files. Access to network will not be provided