I have gone with these post in the WHMCS thread there is nothing where I can find the plugin.
and second link has mentioned below points:
2. This is only a sample and you are using it on your own risk.
3. The code is not written by a PHP programmer so it may not be optimal. Feel free to modify it as you like.
these lines afraid me to use this.
although i have tried but it seems thay have moved the plugin from the provided location:http://whmcstips.com/code/webmoney.zip
. I am getting 404 when trying to download this plugin zip.