How to set up a "child" proxy that doesn't need a "parent" proxy

I run Linux on a laptop that is sometimes on a corporate network which uses an NTLM proxy server, and thus I have cntlmd running on the laptop as a child proxy to connect to the parent (corporate) proxy server. Everything running on the laptop is configured to use localhost:3128 (the CNTLM proxy address) and then cntlmd handles the non-standard authentication with the NTLM proxy server. When I take the laptop off the corporate network, there are maybe a dozen different places things are configured to use localhost:3128, and it is a pain to disable and then later re-enable them. It is apparently not possible to configure cntlmd to not use a proxy when the one it is configured to use is unavailable. One option is to write a script that will automate all these changes for me, but it seems that it might be simpler to have a second child proxy that I can (automatically) start up when cntlm startup fails (it fails if it can't find the parent proxy). The second child proxy would just connect directly to the network, and so if it also listened on 3128 everything configured to hit 3128 could keep its configuration the same. What I can use to do this with? (Or is there a better way?)