I've made and repaired plankton nets from an appropriate grade of nylon
bolting cloth - sorry, can't remember the nomenclature of mesh-sizes and the
name of a British supplier wouldn't be much use to you, but you could try a
biological supplies house or a supplier to the flour-milling or similar
trades. I've used a large nylon flour-sieve for a number of purposes, from
netting macroplankton in shore pools to rough-filtering spring water, but
maybe the pore size is too large for your needs. Tony
N-S.
