By all means – if they do it again this year I will get some for you.
The only thing is – I’ve never seen that ‘pollen’ coming in before or since and I’m not certain that it was poplar leaf rust spores. I suppose the thing to do would be to get some poplar leaves infected with the rust and see if the spores match the stuff the bees were bringing in and the gut contents as well. Or better yet – The Forestry Commission Pathology Dept at Alice Holt should be able to help you – they probably have microscope images of Melampsora spores because it seems to be quite a pest! Contact details here http://www.forestry.gov.uk/fr/ddas
I’d love to see the images of the ‘small structure’ – is there a link to them?

I am a microscopist in London. I recently was given bee gut samples to image. we find in some bees a small structure that we can not agree what it is yet. it is either a parasite or a rust spore of some sort. I wondered if you could send me some of this rust ‘pollen’ next season to analyse for comparison?