There may well be an easy way to do this on Kobo, I just haven't found what it is! From a couple of quick online searches and a scoped search here in MR, I can't find anything about it.

If you have time to check around yourself, it might be worth checking in some of the kobo .config files that are in folders on the device, and see if any of those contain a useragent string that could be tweaked.