I have three complete base rings with door for a Technical Innovations ProDome. I used them while I was building my larger observatory which you can see at my web site (members.home.net/jscala2). These rings are like new, complete and all three can be had for the price of one. The only rub is that you pay for packing materials(I'll supply labor) and shipping. I suspect the shipping costs can be kept quite low.
If you are building a ten foot Technical Innovations Dome, here's a chance to save some money.