Oh wow thanks for all the replies - you guys are the best! I have had a look at the Sworks funnel, it looks amazing. I really liked the suggestion of the cheap one from eBay too, which definitely fulfilled the brief of being cheap and magnetic!
I’m hoping this is going to be something I buy once and use forever, so is probably worth spending a bit more now on the Sworks funnel.
Thanks everyone!
EDIT - Uncletits you have the best username. So much so that I am now looking at Normcore funnels too despite them not having an executive silicone band-thing.