Those are referred to as Split Rims. They were used from late 1925 until the end of Model T production in 1927. They were used with the 21" tires.
Good ones, like a lot of parts, are getting hard to find. Try to find a good one that isn't rusty, has a more or less smooth tire mounting surface and has the latch or screw assembly which holds the split part together and wheel lugs that are not worn out or ovaled.
These were reproduced at some point and I think were about 150.00 from memory. I am not sure if they are still available.
I think a good original rim is easily worth 100.00-150.00 if you need one and you can find one. Try the Model T Ford Club of America forum at
www.mtfca.com
A good swap meet that has a decent amount of prewar parts will usually yield some of these for sale. Prices at swap meets are typically cheaper than online and you won't have to pay for shipping. But, if you need one now and there are no swap meets around you, start searching online.
Model T Haven is a good source for parts. Give Mark a call, he probably has one in stock.
https://www.modelthaven.com/
Lang's Old Car Parts might have some as well, as they have a good inventory of used parts which are not listed in their online catalog. You probably should call for best results.
https://www.modeltford.com/
Hope this helps.