The only 20-30 band parametric Eq's I've ever heard of was made by a company called White Insturments. They went out of business around the mid to late 80's. There's maybe a few on the used market but you'll pay hi $$$ for them still today. Everybody that I heard of that owns one will never give it up, even though they're old eq's.
Look around there's good 5-7 bands per channel parametric eq's market, and if the filter freq. covers a wide range you can combine the 2 channels and have a 10-14 band parametric eq., then it's just a matter of adjusting the Q of the different freq. bands filter. Even though you would have to purchase a second eq. for 10-14 bands in stereo.