You are overthinking-as said above buy a cheapo LRF off Ali express or amazon, it will do the job fine. If you want to spend more buy the Hawke one for a hundred quid or so (I wouldn’t). I used the Ali express one I’ve got until I got an LRF thermal-never in the field tbh, just for setting up zeroing range etc, I also used to take it walking the dog to practice ranging by eye. Would walk along and pick a tree and go 125 metres then ping it and check, was fun and worth doing IMO.
I’d add that unfortunately in reply to your original post a ‘horrendously expensive’ thermal spotter with LRF is going to be about the best thing you can invest in. Try to prevent yourself spending money needlessly and save up the 1500 odd quid you need for one (mine was 1250-got a superb deal on optics warehouse). In the meantime if you must, spend less than 50quid on a cheapo rangefinder.