One other source is EBay. If you watch under chamber insert or chamber adapters a very few come up for sale from time to time. I have seen a few of the old silver style 10/12 sell in the last year.
There is also seller who makes 12/20 adapters and a few others. I tried to get him to make a set of 16/20 adapters for me but he said they were too thin. I suspect he figures thin might fail and he would get sued somehow. Don't see a 10/12 version from him but it might be worth an email and ask him if he makes them.
I bought half a dozen of his 12/20 adapter and turned them down to fit my 16 ga on a metal lathe. So I ended up with a set of 16/20 the hard way. Any good machinist, which I am certainly not, could do the job in just a few minutes.
For low volume the Skeeters are OK. But the aluminum material seems more prone to rapid wear than the steel, which will cause the steel rim shells to stick faster. I had a set of Skeeters but soon decided they would not last long if used heavily.
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=459330119 http://www.ebay.com/itm/2-10-Gauge-to-12...s-/291321823282
