You'll need to find the right package from your distribution which includes
apxs. Your tags include redhat, so you're probably looking for something like
httpd-devel. (I found the package name via Google: in general, packages related to building software will have -dev or -devel in their names.)
Download the correct package on another machine (distribution, machine architecture and version all need to match the version of the httpd package installed on the server), copy the file over, and install it with
rpm -i filename.rpm.
You might find that
rpm complains about missing dependencies; if so, repeat the above for the missing packages. (Yum will handle dependencies automatically; this is one of its advantages!)