X-ways Forensics is way more advanced than R-studio.
That being said, i've only used R-studio once some 5-6 years ago, when i tried it privately.

Maybe give the open source tool a chance, i think they are capable of doing what you need.
There might be a difference in the way each tool is using their regex syntax, the ones i've written in the last post would work for X-ways forensics.

The hex values of the wallet.dat headers I did have some older versions myself, and used them at first to verify.
I asked Chat GPT for every variant of the wallet.dat files from all versions, and it came up with the ones i did not already have myself.

EDIT:

YES, \x is used by X-ways when doing regex searches with hex values, so maybe other tools just used the hex value, you will have to maybe do some test searches to verify that


Image below is the search window in X-ways, in this search i've chosen to search in all objects in the volume (all logical + unallocated area)
Regular expression selected, and the regex search it self.

https://i.postimg.cc/G24FtYgx/regex-wallet.png



YES is does seems like R-Studio uses the same hex syntax as X-Ways
Try and follow the guide you linked to, and create a custom signature with the regex information I posted earlier.
The signature is the header, there is not any known signature for the files end, so it needs to be empty i would assume (this is very typical, not to have an ending signature)