Did you sort this? The required length makes it more tricky. Only one that springs to mind is Insensibility, Wilfred Owen's long poem about the way soldiers need to shut off their emotions to cope with the horrors of war. I suppose there is a link here to Catch 22 as it is anti-war and about emotional effects of war, but it is years since I read either. Maybe not the best choice.
You could try doing a search for poems/poets to compare with the themes in the novel? Anti-bureaucracy, insanity, insanity of war, Catch-22 situations etc. Then select by length.
There is The Wasteland but it is very long, obscure and complex.