Cannot uninstall SupportAssist

I've been trying to uninstall Support Assist so as to reinstall it, because the application has not been working for some time.

I get the following error message when I try to uninstall:

"The feature you are trying to use is on a network resource which is unavailable.

Click OK to try again, or enter an alternate path to a folder containing the installation package 'SupportAssistx64-2.2.2.7.msi' in the box below"

I can't find the installation file referenced in the error message, online or on my computer, and it was installed from a local copy, not a networked drive. At the moment I can't uninstall the application.

Can anyone help me either find this file or find a workaround which would allow me to uninstall it?