There is an upstream deb (Debian installer file) which you can download to install it. However it is an all-in-one type installer so will include lots of modules that will be irrelevant to your server (hence why TKL build their own with all the separate modules split into individual installers).
If you do go with the upstream version I'm not sure if the TKLBAM module will work with it (but you could always try I guess...). Regardless, make sure that you remove the existing Webmin first (and then try to reinstall the TKLBAM module once you have installed the new Webmin).
You can install from upstream
There is an upstream deb (Debian installer file) which you can download to install it. However it is an all-in-one type installer so will include lots of modules that will be irrelevant to your server (hence why TKL build their own with all the separate modules split into individual installers).
If you do go with the upstream version I'm not sure if the TKLBAM module will work with it (but you could always try I guess...). Regardless, make sure that you remove the existing Webmin first (and then try to reinstall the TKLBAM module once you have installed the new Webmin).