Where are you?
I have sailed half the Oz coast and most of the islands in Eastern PNG and hardly seen a mozzy or midge. One skipper
did get malaria but he got bitten on an island hanging out with the locals.
Being paranoid about malaria I always light a knockdown coil when first sighting a mozzy (rare). Never had a problem with coils.
A net would sure be good to have but can't help you souce a good one.
Always try to anchor
far enough off shore not to attract them and don't hang out on land sunrise/set. Don't like spraying deet on my body but after seeing skip with malaria I think I might carry spray and use it if nessasary.
You can use velcro on netting to attach to hatches and just drape something over companioway.