I am trying to put a shutoff valve on a toilet supply line. The fitting coming out of the floor is a 3/8″ compression male thread. I am looking for a bushing with a 3/8″ female compression thread and a 3/8″ or 1/2″ male mpt thread. The only valves I can find have a 3/8″ female thread
Personally I would take out that compression fitting and solder in a Copper Male adapter THEN screw on a new FIPS Valve compression.
If you need to get in and get out as fast and cheap as possible and could careless about doing the right thing you can do the following.
Get a small piece of copper 3/8 diameter and another compression Male adapter.
Using this short piece of copper in between the two compression fittings you will now have a male thread to work with to install a new FIPS Valve by compression so you can continue with this really bad job, BUT it will get you out of replacing the fitting and doing the job properly