I was in the same boat a few years back with attempting to locate a production "shooters box." I met a very generous man retiring from Virginia PPC who helped me out and sold me one of his boxes. I still use that box today in my PPC matches.
In early 2009 I made contact with Roy Myers. Myers has/had a business named Hole in the Wall Firearms Training School, 2508 E. Dunkin Road, Cushing, OK 74023, 918-387-4150. I do not know if Myers is still in business today but I thought I would make this posting to help a new shooter.
At that time Myers only had a hand full of the shooters boxes left which included a carrying case for extra ammo, etc. The best set up I had seen and the only one out there on the market. Border Patrol and US Custom made a large purchase just prior to my order. Myers indicated that it was difficult to get the boxes made by his undisclosed contact company that owned the original molds for the boxes. Myers was tight lipped as to the name of the company that held the molds and I don't blame him. Myers was trying to have more boxes made to do a service for PPC shooters and make a profit in his business. Draw back was the outlay of capital due to the number of boxes that must be made to make it worth moving forward.
I purchased from Myers a few boxes for my PPC team members and a couple of other shooters here in Maryland. We bought the boxes as spared in the event that something happen to our older boxes. They are not for sale at this time. At @$45 each plus shipping Myers was not making much money and had to sell hundreds to make it worth effort. PPC in recent years has declined due to a number of factors not discussed here. That for another discussion. NRA's Marc Lipp is working hard to improve PPC and bring the sport back.
You have already read that the loading blocks for L and K frame revolvers are still available today from Safariland. Brownells has them as mentioned. I like the idea of the box mentioned at Homedepot. I have seen similar boxes on the firing line at matches that do the job. Now days anything would work as long as you where not carrying a suitcase up to the line. The box does not make the shooter but it would be nice if you could find one for sale. Every now and then you will find one for sale but they go quick. Networking! I feel unless you find some one retiring from PPC, I doubt you will ever find them sold new on the open market. The cost of production is significant for the return on the money, otherwise, the boxes would be available to day.
Good luck in your search for a shooters box and may you one day shoot a perfect 1500 with 150X! OC COP