The first thing I do when I can't immediately find something, is to locate the command in the programming manual, open the VI Tree, and do a text search. I did this for the command SRAT and found it in hpesgdxx Config Dual Arb. I have no idea if this is the command you need. The instrument is very complex with all of the different options. The programming manual is in 3 volumes!
If you can't find the command in the driver, then you can implement your own function and add it to the driver. That is one of the reasons NI provides the source code for all of their drivers and why I would recomend you use the LabVIEW driver. Creating a new function for the driver is usually pretty simple and you have the rest of the driver to use as a template. Anyone who is using LabVIEW in the first place should be able to do this. Since you already have the IVI driver, a quick way to learn the necessary SCPI commands is to turn on NI-Spy, run the IVI function, and copy the command from the capture.
To try to get the driver modified by NI, there is the 'Give Driver Feedback' link at the top of the download page. I don't know how long it would take to get an updated driver.
