MCatSHF

I bought mine locally many years ago. They spin right into the drum threads very easily if anything maybe a tiny bit loose. 

The funnel itself does screw onto the bung adapter on the ones I have and it has seeped a little over time probably just take it apart and put a little RTV on the threads and put it back together.

I collect oil out of machines in 5 gallon buckets most of the time or a half bucket for vehicles due to less clearance. Pour it right into the barrels while it's still pretty hot funnels seem to handle that okay just be sure to vent the drum with the small bung being opened or it will burp out out of the big funnel and make a mess.

The top lip of the funnel and sides are not very rigid either so you cannot really rest a bucket against it while pouring. As long as you are steady and pour the bucket at a controlled rate it will keep up pretty good. 

The top of the funnel is about 8" across as you can see it is big enough to set a large tractor oil filter in it to drain.

Also here it is how it compares in size to the bottom of a cut off regular 5 gallon bucket.

Another thought.

You could take a 5 plastic gallon bucket and cut the top 1/2 with the handle off drill a hole in the bottom in the middle of the reinforcing ring and use a 2" plastic spray tank bulkhead fitting with gaskets and make your own screw on drum funnel.

Might work better with a steel bucket if you can find one (bulk grease ? ) or a large steel mixing bowl like I use for small engines.  That would be a smooth bottom with no reinforcing ribs like on the plastic bucket.  Only drawback is it would not empty completely. Would look something like this. 

I'd like to find some of those round drum absorbent pads like in your link.

Edit:

Looks like the pads are here but sort of steep at over $2 ea. and you have to buy 25

http://www.amazon.com/SpillTech-BTOP-Polypropylene-Oil-Only-Diameter/dp/B009CHYK4E