I've been playing around with such modules for years. I have at least 10 of them because I use them so much, and have often wanted a faster speed. Sadly I have been unable. They all make use of a USB chip which is programmable, but it gets very technical. There is certainly no way to do it through windows or the serial interface. Saying that, I've been buying cheapo modules from eBay - probably 5 or 6 different types. I know there are modules where you can configure the baud rate, but they are far more expensive - I believe the cheap modules were designed for a specific purpose which never got used in the product they were designed for.
I suggest you look at datasheets for all the chips on the module, and see which are programmable, and how they can be programmed. It may not be possible without de-soldering the chip(s) from the modules and programming them using the development kits and/or programmers.
For cheap options, you might want to look at bluetooth modules which are designed for faster digital data such as audio - but then they will not register as serial data dongles from the USB side, so you may have to jump through hoops on the PC side to make a software adaptor that hi-jacks the audio and makes it available as serial data.
The modules I've bought tend to have a baud anywhere between 1200 and 9600, so if you pick up a few of them, you might get one that is at the lower baud you want. But at that point, you might as well buy one from a decent source where they guarantee the baud is configurable (and has instructions on how to do so).