Is there anything special about the BMW Oil Filter removal tool for the K100.  Can I buy an equivalent from SuperCheap, etc ?

OZHoppo

I don't believe so. They are a bit of a trap the various filters available.
I was using framm but found the tool didn't fit because of the different number of flats on the tool and filter and have been using HiFlo because they fit the tool.
What I did to remove the framm filters was drill a 8mm hole in the removal tool and belt a pointed object like a ground to suit bolt through the hole and into the filter then unscrew it.
There are all sorts of filter removal tools but none that fit except for the OEM type.
You can remove the sump and not just the access plate and then get at the filter with an ordinary tool, there is no gasget just use 3 bond or permatex blue when you replace it.

As described below you can easily and cheaply make an oil filter wrench:

Take a piece of PVC pipe of 75 mm diameter and + / - 20 cm length; (photo 1)
Warm one end of the PVC pipe to the inside and outside well, for example an electric heat gun (up to 1200W about 2 minutes) over a width of ~ 3 cm so that it is soft; (photo 2)
Slide the PVC pipe now on a old (or new) oil filter;
Let the PVC pipe now cool and it fits perfectly;
Now remove the PVC pipe from the filter; (photos 3 and 4)
Drilling,  2 holes in the pipe.  Loose the filter with a screwdriver inserted

Good work Dutchie!