Spend the money having someone machine polish it 
^+1. My previous car was parked up on a hot, sunny day and one of our feathered ‘friends’ used it for target practice. By the time I’d got back to my car, the bird poo was well and truly baked on to the paintwork. I’ve got my own machine polisher and a few minutes effort using an appropriate combination of pad and polish and all signs of etching were removed.
@Harry213; I’ve no experience of Autoglym Reflow - I think it’s aimed at professionals, although as you’ve found, professional products do turn up for sale on certain well known online auction sites. I’ve seen YouTube videos of people using a heat gun to remove bird poo etching, although I would never be brave enough to do that to my car! Autoglym Reflow probably works using the same principle - i.e. using heat - but through a thermal reaction - to remove etch marks.
If you are happy to give a rough idea of your location and wait until lockdown restrictions are lifted, there may be a forum member who’s a detailing enthusiast with a machine polisher who lives in the same area as you that could sort the etching out for a few beer tokens. From your picture, it looks as if machine polishing will correct it fairly easily - it certainly looks much less severe than the etching damage I polished out on my last car.
