The easel in your picture is the Yarka "Russian French Easel" that was distributed in the US for a short while during the ninties. I bought mine about 15 years ago from Jerry's Artarama. Jack Richeson & Co. also carried them for awhile. Don't know why no one distributes it now, many yarka products are still sold in the US.
Yarka had a large and a medium easel. I have the medium easel and there is a label so I Googled the name of the Russian manufacture, Podolsk-Art and found this listing on ebay but it was sold in Feb. Looks like the seller deals in easels, if you have an ebay account you can contact them and see if they have more.
It was distributed in the US by:
Essex, MA 01929
I didn't find anything on the internet for Postport Inc.
Antonin,I would appreciate you letting me know if you find one, If not, I might be able to help. Good Luck