I've used Flash Drives with MS-DOS.
I would be interested to know how you did that. AFAIK, there is no USB support for native MS, or IBM, DOS. I believe that DR-DOS does have some USB support.
For warp 4, you do need the latest available updates, to have any hope of using a modern Flash drive. The CWUSB package is also a possibility, but, in both cases, you will, probably, be restricted to using devices from the late 20th century, and not all of them will work. The newer USB support, that actually works, is available only for eComStation.
I just bought the OS and it has nothing working, why put more money in?
You just bought an antique, that will actually work quite well, with a bit of tweaking, but it has little support for anything from the 21st century. On the other hand, if you can locate newer device drivers, most of them will work with warp 4.
So if the IBM Driver is not freely available, is there an alternative?
The CWUSB driver is the alternative, but the latest available (for warp 4), drivers are probably better, since CWUSB is older.
I guess the first question, that I have, is: Have you installed ALL of the software maintenance that is available? I think you should be able to find most of it by following links at:
http://www.passtheshareware.com/os2.htmalong with some links to help pages etc. (Note, that this is not a complete list, but should get you started). Of course, the easy way to get OS/2 to work, is to purchase eComStation. Unfortunately, eCS doesn't have support for everything, simply because there aren't enough people working to do it, and manufacturers don't want to make their little secrets available, so people can make some things work properly (probably ashamed of the quality of their products).